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Biomedical subjects

J Whelan

Publications and source records attributed to J Whelan.

At least 19 recordsLinked to original sources
PubMed1999

Import of precursor proteins into mitochondria from soybean tissues during development.

Characterisation of the amount of protein import of the alternative oxidase (AOX) and the F(A)d precursor proteins (previously shown to use different import pathways) into mitochondria from developing soybean tissues indicated that they displayed different patterns. Import of the AOX declined in both cotyledon and root mitochondria with increasing age, whereas the import of the F(A)d into cotyledon mitochondria remained high throughout the same period. Using primary leaf mitochondria, it was evident that import of AOX remained high while it declined in cotyledon and root mitochondria. The amount of import of the AOX into mitochondria from different tissues closely matched the amount of the Tom 20 receptor.

Biological Transport, Active↗
PubMed1999

Decreased activity of the L-arginine-nitric oxide metabolic pathway in patients with congestive heart failure.

BACKGROUND: Impaired endothelium-dependent, nitric oxide (NO)-mediated vasodilation may contribute to increased vasomotor tone in patients with heart failure. Whether decreased endothelium-dependent, NO-mediated vasodilation in patients with heart failure is due to decreased synthesis or increased degradation of NO is unknown. METHODS AND RESULTS: To specifically assess the synthetic activity of the L-arginine-NO metabolic pathway, urinary excretion of [15N]nitrates and [15N]urea was determined after a primed continuous intravenous infusion of L-[15N]arginine (40 micromol/kg) in 16 patients with congestive heart failure and 9 age-matched normal control subjects at rest and during submaximal treadmill exercise. After infusion of L-[15N]arginine, 24-hour urinary excretion of [15N]nitrates was decreased in patients with congestive heart failure at rest (2.2+/-0.5 versus 8.0+/-2.3 micromol/24 h) and during submaximal exercise (2.4+/-1.2 versus 11. 4+/-4.0 micromol/24 h) compared with control subjects (both P<0.01). After infusion of L-[15N]arginine, 24-hour urinary excretions of [15N]urea at rest in patients with congestive heart failure and control subjects were not different (1.1+/-0.3 versus 1.2+/-0.2 mmol/24 h, P>0.20). CONCLUSIONS: A specific decrease in synthetic activity of the L-arginine-NO metabolic pathway contributes to decreased endothelium-dependent vasodilation in patients with congestive heart failure.

Adult↗
PubMed1999

Signals required for the import and processing of the alternative oxidase into mitochondria.

The critical residues involved in targeting and processing of the soybean alternative oxidase to plant and animal mitochondria was investigated. Import of various site-directed mutants into soybean mitochondria indicated that positive residues throughout the length of the presequence were important for import, not just those in the predicted region of amphiphilicity. The position of the positive residues in the C-terminal end of the presequence was also important for import. Processing assays of the various constructs with purified spinach mitochondrial processing peptidase showed that all the -2-position mutants had a drastic effect on processing. In contrast to the import assay, the position of the positive residue could be changed for processing. Deletion mutants confirmed the site-directed mutagenesis data in that an amphiphilic alpha-helix was not the only determinant of mitochondrial import in this homologous plant system. Import of these constructs into rat liver mitochondria indicated that the degree of inhibition differed and that the predicted region of amphiphilic alpha-helix was more important with rat liver mitochondria. Processing with a rat liver matrix fraction showed little inhibition. These results are discussed with respect to targeting specificity in plant cells and highlight the need to carry out homologous studies and define the targeting requirements to plant mitochondria.

Amino Acid Sequence↗
PubMed1999

Relationship of beta-catenin and Bcl-2 expression to sulindac-induced regression of intestinal tumors in Min mice.

Non-steroidal anti-inflammatory drugs (NSAIDs) can cause regression of early intestinal tumors and although this is believed to involve cyclooxygenase-2 and apoptosis, the molecular mechanisms remain unclear. Cytoplasmic and nuclear beta-catenin are overexpressed in many of these lesions and Bcl-2, which inhibits apoptosis, may also be elevated during the course of intestinal tumorigenesis. We recently showed that sulindac causes regression of 70-80% of small intestinal tumors in Min/+ mice within 4 days, but does not have the same impact on colonic lesions; after 20 days of treatment the tumor load stabilizes at 10-20% of that in untreated animals. The aim of this study was to determine if NSAID-induced regression of intestinal adenomas might be associated with changes in beta-catenin or Bcl-2 expression. Intestinal tumors from Min/+ mice were harvested after treatment with sulindac for 2, 4 or 20 days and evaluated for expression of beta-catenin and Bcl-2 using immunohistochemistry. There was a > or = 50% decrease in beta-catenin (P = 0.001) and diminishing Bcl-2 (P = 0.019) in small intestinal tumors harvested between 2 and 4 days of treatment when compared with untreated controls. In contrast, small intestinal tumors from animals treated for 20 days were not significantly different from untreated controls. Colonic tumors expressed higher levels of Bcl-2 than those from the small intestine and did not show any significant changes in either Bcl-2 or beta-catenin expression after treatment. Results suggest that modulation of aberrant beta-catenin expression occurs during NSAID-induced regression of intestinal adenomas and that Bcl-2 may confer resistance to these effects.

Adenoma↗
PubMed1999

Neoadjuvant chemotherapy with doxorubicin and cisplatin in malignant fibrous histiocytoma of bone: A European Osteosarcoma Intergroup study.

PURPOSE: Studies involving small case series have suggested that malignant fibrous histiocytoma of bone (MFH-B) is a chemosensitive tumor and that chemotherapy may improve survival. In this study, we evaluated clinical and pathologic response rates and survival in a series of patients treated with a consistent chemotherapy regimen of doxorubicin and cisplatin (DOX/DDP). PATIENTS AND METHODS: Study patients were required to have biopsy-proven MFH-B, no previous chemotherapy, and primary or metastatic measurable disease and to be </= 65 years of age. Treatment consisted of doxorubicin 25 mg/m(2)/d days 1 through 3 and cisplatin 100 mg/m(2) by 4-hour intravenous infusion every 3 weeks for six cycles. In patients with operable primary tumors, chemotherapy was planned to start within 42 days of biopsy, with definitive surgery performed after three cycles. RESULTS: Forty-one patients had operable nonmetastatic limb sarcomas, and 23 (56%) completed six chemotherapy cycles. Limb salvage was possible in 33 patients (80%), and 16 (42%) of 38 assessable specimens showed a good pathologic response (>/= 90% necrosis). Median time to progression was 56 months, and the 5-year progression-free survival rate was 56% (95% confidence interval [CI], 40% to 72%). Median survival time was 63 months, and the 5-year survival rate was 59% (95% CI, 41% to 77%). Patients with a good pathologic response had longer survival times and times to progression than did those with a poor response. Also treated were two patients with locally recurrent and nine with metastatic disease, and these patients had a median survival time of 17.5 months. CONCLUSION: Our study suggests that adjuvant or neoadjuvant chemotherapy with DOX/DDP is beneficial in MFH-B. Good pathologic response rates and survivals are quite comparable with those for osteosarcoma, a related bone tumor for which adjuvant or neoadjuvant chemotherapy is an accepted practice.

Adolescent↗
PubMed1999

Single-step method for the determination of the amount of the common deletion in mitochondrial DNA.

A fluorescent-based quantitative PCR assay to measure the percentage of the common deletion in rat mitochondria is reported. The amount of the common deletion is measured relative to the amount of total mitochondrial (mt)DNA. The use of a heterologous competitor construct allows the reaction to be monitored to ensure that exponential accumulation of products occurs. The use of fluorescence-labeled primers provides a safe and sensitive means to quantify products without any adjustment for size. This assay will allow the quantitative determination of the common deletion with one dilution range.

Animals↗
PubMed1999

Measurement of DNA cross-linking in patients on ifosfamide therapy using the single cell gel electrophoresis (comet) assay.

The single cell gel electrophoresis comet assay has become established as a sensitive technique for measuring DNA strand breaks. The technique has been modified to allow the sensitive detection and quantitation of DNA interstrand cross-linking at the single cell level. Cells are irradiated immediately before analysis to deliver a fixed level of random strand breakage. After embedding of cells in agarose and lysis, the presence of cross-links retards the electrophoretic mobility of the alkaline denatured cellular DNA. Cross-links are, therefore, quantitated as the decrease in the comet tail moment compared with irradiated controls. Using this method, a linear response of cross-linking versus dose of chlorambucil over a wide dose range was demonstrated in human lymphocytes after drug treatment ex vivo. The method was also sensitive enough to determine cross-linking in clinical samples after chemotherapy. For example, crosslinking was observed in the lymphocytes of patients receiving ifosfamide (3 g/m2/day) as a continuous infusion for 3-5 days or as a 3-h infusion daily for 3 days. Cross-links were detected in all patients within 3 h, with no evidence of DNA single strand break formation. In patients receiving continuous infusion, a plateau of cross-linking was reached by 24 h. In the patients receiving ifosfamide over 3 h, a clear decrease in the peak level of cross-linking was observed before subsequent infusions.

Antineoplastic Agents, Alkylating↗
PubMed1999

Colorectal cancer in adolescents.

Colorectal cancer, one of the most common malignancies among adults, is rare in adolescence. This low incidence coupled with non-specific symptoms and aggressive natural history leads to a poorer prognosis than in reported adult series. This article describes two cases of colorectal cancer in adolescents and reviews the literature regarding this rare condition. Earlier diagnosis and a greater understanding of the natural history may lead to improved treatment with concomitant improvements in survival.

Adenocarcinoma↗
PubMed1998

Identification of a novel stress activated kinase in kidney and heart.

We have previously described the patterns of stress kinase activation in rat kidney and heart in response to ischemia/reperfusion (Yin et al., 1997, J. Biol. Chem. 272, 19943-19950). During the course of these studies, we observed the activation of a novel kinase capable of phosphorylating c-Jun on serines 63 and 73. The molecular weight of this kinase is approximately 37 kD, significantly below the molecular weight of all previously identified Jun N-terminal kinase (JNK) isoforms. The pattern of activation of this 37 kD kinase in response to ischemia/reperfusion in both kidney and heart is distinct from that of known JNK isoforms. Western analysis of human renal proximal tubular epithelial (RPTE) cells, using a non-isoform specific phospho-JNK antibody, revealed the phosphorylation (activation) of a 37 kD protein in response to hypoxia. The 37 kD protein in RPTE cells is phosphorylated by other stress stimuli capable of activating JNK. Western analysis of tissues, using a non-isoform specific JNK antibody, identifies a cross-reactive 37 kD protein expressed in the liver, thymus and lymph node which is likely to correspond to the 37 kDa stress-activated kinase. The results of this study have led to the identification of a potentially novel kinase closely related to JNK but showing a distinct pattern of activation.

Animals↗
PubMed1998

Assessment of the arachidonic acid content in foods commonly consumed in the American diet.

Arachidonic acid (AA) is an extremely important fatty acid involved in cell regulation. When provided in the diet, it is cogently incorporated in membrane phospholipids and enhances eicosanoid biosynthesis in vivo and in vitro; however, controversy exists as to the levels of AA in food and in the diet. This study determined the amount of AA in cooked and raw portions of beef (rib eye), chicken (breast and thigh), eggs, pork (loin), turkey (breast), and tuna; it compared these results to values published in Agriculture Handbook No. 8 (HB-8). The cooked portions were prepared as described in HB-8. With the exception of chicken thigh and tuna, the levels of AA (w/w) in the selected foods analyzed were significantly higher, in general, than those values published in HB-8. The greatest differences were observed in beef (raw and cooked), turkey breast (raw and cooked), and pork (cooked) where AA levels were twice that of the values in HB-8. In contrast, the AA and n-3 fatty acid contents in tuna were almost half the HB-8 values. The present data indicate that HB-8 tends to underreport the amounts of AA in a number of foods commonly consumed in the American diet, and new initiatives should be considered to validate and update the current database for fatty acid composition of foods.

Arachidonic Acid↗
PubMed1998

Random mutagenesis of human estrogen receptor ligand binding domain identifies mutations that decrease sensitivity to estradiol and increase sensitivity to a diphenol indene-ol compound: basis for a regulatable expression system.

We have used low fidelity polymerase chain reaction amplification to generate mutations in the human estrogen receptor ligand binding domain (LBD). Screening of libraries of mutants in yeast revealed a variety of phenotypic changes including decreased responsiveness to estradiol and increased responsiveness to synthetic compounds. Identification of the mutations responsible for these phenotypic changes indicated discrete regions of the LBD that are important for human estrogen receptor function. Cumulative rounds of mutagenesis and screening allowed us to produce a mutant estrogen receptor that was of reversed specificity as compared with the wild type LBD, in that it was more responsive to a diphenol indene-ol than to estradiol. This mutant may form the basis of a useful regulatable expression system in mammalian cells.

Amino Acid Sequence↗
PubMed1998

A matrix-located processing peptidase of plant mitochondria.

Nuclear-encoded mitochondrial precursor proteins are proteolytically processed inside the mitochondrion after import. The general mitochondrial processing activity in plant mitochondria has been shown to be integrated into the cytochrome bc1 complex of the respiratory chain. Here we investigate the occurrence of an additional, matrix-located processing activity by incubation of the precursors of the soybean mitochondrial proteins, alternative oxidase, the FAd subunit of the ATP synthetase and the tobacco F1 beta subunit of the ATP synthase, with the membrane and soluble components of mitochondria isolated from soybean cotyledons and spinach leaves. A matrix-located peptidase specifically processed the precursors to the predicted mature form in a reaction which was sensitive to orthophenanthroline, a characteristic inhibitor of mitochondrial processing peptidase (MPP). The specificity of the matrix peptidase was illustrated by the inhibition of processing of the alternative oxidase precursor in both soybean and spinach matrix extracts upon altering a single amino acid residue in the targeting presequence (-2 Arg to Gly). Additionally, there was no evidence for general proteolysis of precursor proteins incubated with the matrix. The purity of the matrix fractions was ascertained by spectrophotometric and immunological analyses. The results demonstrate that there is a specific processing activity in the matrix of soybean and spinach in addition to the previously well characterized membrane-bound MPP integrated into the cytochrome bcl complex of the respiratory chain.

Cell Nucleus↗
PubMed1998

Mitochondrial protein import in plants. Signals, sorting, targeting, processing and regulation.

Mitochondrial biogenesis requires a coordinated expression of both the nuclear and the organellar genomes and specific intracellular protein trafficking, processing and assembly machinery. Most mitochondrial proteins are synthesised as precursor proteins containing an N-terminal extension which functions as a targeting signal, which is proteolytically cleaved off after import into mitochondria. We review our present knowledge on components and mechanisms involved in the mitochondrial protein import process in plants. This encompasses properties of targeting peptides, sorting of precursor proteins between mitochondria and chloroplasts, signal recognition, mechanism of translocation across the mitochondrial membranes and the role of cytosolic and organellar molecular chaperones in this process. The mitochondrial protein processing in plants is catalysed by the mitochondrial processing peptidase (MPP), which in contrast to other sources, is integrated into the bc1 complex of the respiratory chain. This is the most studied component of the plant import machinery characterised to date. What are the biochemical consequences of the integration of the MPP into an oligomeric protein complex and how are several hundred presequences of precursor proteins with no sequence similarities and no consensus for cleavage, specifically cleaved off by MPP? Finally we will address the emerging area of the control of protein import into mitochondria.

Amino Acid Sequence↗
PubMed1998

Differential expression of alternative oxidase genes in soybean cotyledons during postgerminative development

The expression of the alternative oxidase (AOX) was investigated during cotyledon development in soybean (Glycine max [L.] Merr.) seedlings. The total amount of AOX protein increased throughout development, not just in earlier stages as previously thought, and was correlated with the increase in capacity of the alternative pathway. Each AOX isoform (AOX1, AOX2, and AOX3) showed a different developmental trend in mRNA abundance, such that the increase in AOX protein and capacity appears to involve a shift in gene expression from AOX2 to AOX3. As the cotyledons aged, the size of the mitochondrial ubiquinone pool decreased. We discuss how this and other factors may affect the alternative pathway activity that results from the developmental regulation of AOX expression.

Journal Article↗
PubMed1997

Sulindac causes rapid regression of preexisting tumors in Min/+ mice independent of prostaglandin biosynthesis.

Several lines of evidence strongly link prostaglandins (PGs) and leukotrienes (LTs) to cancer of the intestine. Several studies have reported a 40-50% reduction in mortality from colorectal cancer in individuals who routinely consume nonsteroidal anti-inflammatory drugs, possibly by inhibiting cyclooxygenase activity. However, the role of eicosanoids in this process is still unclear. The heterozygote Min/+ mouse model, like patients with familial adenomatous polyposis, carries a nonsense mutation in the adenomatous polyposis coli (APC) gene that results in the spontaneous development of intestinal adenomas (100% incidence). This study investigated the association between eicosanoid biosynthesis, intestinal tumor load, and the chemotherapeutic effect of the nonsteroidal anti-inflammatory drug sulindac during early and preexisting phases of tumor growth and development as well as residual effects after drug withdrawal. Administration of sulindac (320 ppm) to Min/+ mice reduced the tumor number by 95% but did not alter the levels of PGE2 and LTB4 in intestinal tissues. Increasing PGE2 and LTB4 levels by 44% with dietary arachidonic acid supplementation had no effect on tumor number or size. When sulindac was added to the arachidonic acid-supplemented diet, tumor number was reduced by 82%, whereas eicosanoid levels remained elevated. In Min/+ mice with established tumors, treatment with sulindac for 4 days reduced tumor number by 75%, and continual administration of sulindac was necessary to maintain a reduced tumor load. In summary, alterations in eicosanoid formation were not correlated with tumor number or size in the Min/+ mouse model; thus, the antitumor effect of sulindac seems to be PG independent.

Adenomatous Polyposis Coli↗
PubMed1997

Temporal regulation of in vitro import of precursor proteins into tobacco mitochondria.

Protein import into isolated tobacco mitochondria was investigated using mitochondria from leaves harvested at different times of the day and night. Efficient import was only detected with mitochondria isolated from leaves harvested during the dark period of the growth cycle, only low levels of import were detected from leaves harvested during the light period. However, this temporal difference seen in import did not appear to be circadian in nature. This implies that the protein import process in mitochondria isolated from leaves is not constitutive. This has important implications for targeting specificity studies performed in transgenic plants, as unless the plants are tested at the time when import is occurring, the true in vivo targeting abilities of chimeric constructs will not be measured.

Biological Transport↗