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D Schofield

Publications and source records attributed to D Schofield.

36 records · Page 2Linked to original sources
PubMed1993

Some pitfalls in the measurement of blood glutathione.

1. We report some pitfalls in the measurement of whole blood and plasma glutathione in man. 2. Using a simple tourniquet to the forearm and a 21-gauge needle, blood samples were collected by brachial vein puncture from healthy subjects. Whole blood and plasma were analysed for total glutathione, including the reduced and oxidized forms, by a spectrophotometric recycling method involving the glutathione reductase/NADPH couple. 3. The concentration of oxidized glutathione was determined after treatment of aliquots with either 2-vinylpyridine or N-ethylmaleimide to trap reduced glutathione. Reduced glutathione in the native samples could then be obtained by subtraction. 4. When the reagents were added to separated plasma, 2-vinylpyridine yielded values for oxidized glutathione that were twice as high as with N-ethylmaleimide. In whole blood studies the discrepancy was even greater, and the problem was not resolved by deproteinization of samples with 5-sulphosalicylic acid. Using N-ethylmaleimide, levels of oxidized glutathione were less than 1% of total glutathione in whole blood. 5. Despite attempts to minimize haemolysis, lysed erythrocytes contributed on average 25% to the 'plasma' glutathione concentration.

Blood Specimen Collection↗
PubMed1993

Nerve growth factor receptor expression in medulloblastomas and the potential role of nerve growth factor as a differentiating agent in medulloblastoma cell lines.

Nerve growth factor (NGF) has the potential to induce cellular differentiation in various neoplastic and nonneoplastic cell lines. In this study, our aim was to determine NGF receptor (NGFr) status in medulloblastoma specimens and cell lines and to investigate whether NGF could act as a potential differentiating agent for this common pediatric brain tumor. Paraffin-embedded tumor tissue from 10 patients with the diagnosis of medulloblastoma was retrospectively analyzed to determine the frequency of NGFr expression. Of the 10 tumor specimens evaluated, 4 were positive for NGFr; however, NGFr staining was confined to only 5 to 8% of the cells in a randomly scattered pattern. No colocalization was present with neuronal, glial, or vascular structures. In addition, two medulloblastoma cell lines established in our laboratory were also evaluated for NGFr. In this study, we also examined the effects of retinoic acid, 12-O-tetradecanoyl-phorbol-13-acetate, and NGF on medulloblastoma cell lines to evaluate their effect on morphological differentiation and NGFr expression. Although these agents failed to cause NGFr expression in our cell lines, morphological alteration was noticed in only one of the cell lines with retinoic acid. Therefore, because of the lack of de novo or induced NGFr expression, it is unlikely that NGF will be useful as a potential therapeutic differentiating agent for medulloblastomas.

Adolescent↗
PubMed1993

Micronutrient antioxidant status in tropical compared with temperate-zone chronic pancreatitis.

Micronutrient antioxidants interact with glutathione in tissues to facilitate the disposal of reactive oxygen species and xenobiotic metabolites derived via cytochromes P450. Published evidence linking cytochrome P450I induction with chronic pancreatitis therefore led us to compare antioxidant status in patients at Manchester in the northwest of England and at Madras in the southeast of India. Serum studies in healthy volunteers showed that the biologic availabilities of selenium and alpha-tocopherol were equally high in the two zones but that the availabilities of beta-carotene and ascorbic acid were lower in the tropical area (p < 0.001), where the ratio of ascorbic acid to total vitamin C concentration in serum was substantially reduced (p < 0.001). The serum antioxidant profiles of the chronic pancreatitis groups reflected these indigenous differences: a decrement in selenium and alpha-tocopherol was evident in both zones, whereas beta-carotene and ascorbic acid values were subnormal only in the Manchester group. The concentration of inorganic sulphate in urine--an index of long-term intake of sulphur amino acids for synthesis of glutathione and other detoxifiers--was similar in controls and patients from Manchester, but levels were lower than in their Madras counterparts (p < 0.02, p < 0.01, respectively). The results suggest that culinary practices that erode the biologic availabilities of ascorbic acid and beta-carotene may predispose to pancreatic oxidative stress and thereby to the changes leading to chronic pancreatitis at an early age in south India. These findings have implications for treatment and prophylaxis.

Adolescent↗
PubMed1993

Immunohistochemical localization of Trk receptor protein in pediatric small round blue cell tumors.

Expression of Trk protein has been documented by Northern analysis in neuroblastomas with good prognosis. To localize the expression of this protein at the cellular level within individual tumors, we adapted a recently characterized pan-Trk antibody for use in formalin fixed, paraffin-embedded tissue. We have examined a group of small round blue cell tumors occurring in children, including both high and low stage neuroblastomas, to assess the presence or absence of Trk expression and its cellular localization. Positive staining for Trk protein was observed in four of four low stage (good prognosis) neuroblastomas, five of five primitive neuroectodermal tumors/Ewing's sarcoma, five of five rhabdomyosarcomas, and no lymphomas. Within the neuroblastomas, expression of Trk protein was most striking in ganglion cells, in which positive cytoplasmic staining was demonstrated regardless of tumor stage. The latter observation may lend further insight into the pathobiology of this malignant childhood tumor.

Antibodies↗
PubMed1992

Differentiation of a primitive neuroectodermal tumor into a benign ganglioglioma.

We describe a case of cerebellar neuroblastoma with histologic documentation of maturation into a ganglioglioma sixteen months later. Only chemotherapy was administered following the initial surgery and the child is well and disease-free three years following her final surgical procedure. The outcome of this patient supports previous hypotheses that the cerebellar neuroblastoma may be a less malignant tumor than its other primitive neuroectodermal posterior fossa counterparts. Furthermore, this case suggests a role for second-look surgery in the management of selected pediatric brain tumors.

Cell Differentiation↗
PubMed1992

Antioxidant therapy for recurrent pancreatitis: biochemical profiles in a placebo-controlled trial.

The usefulness of micronutrient antioxidant therapy for recurrent (non-gallstone) pancreatitis has recently been endorsed by a 20-week double-blind double-dummy cross-over trial in 20 patients. Treatment was delivered as two types of tablets, providing daily doses of 600 micrograms organic selenium, 9000 i.u. beta-carotene, 0.54 g vitamin C, 270 i.u. vitamin E and 2 g methionine. We report antioxidant profiles in blood samples collected before entry, at the cross-over stage and upon completion of trial. Baseline serum concentrations of selenium, beta-carotene and vitamin E in the patients were significantly lower than in healthy controls, were unaltered by placebo and normalized by active treatment, but reverted to basal values in the subgroup that received placebo subsequently. The baseline serum concentration of a free radical marker--the 9-cis, 11-trans isomer of linoleic acid--was significantly higher in the patients than in controls, fell inexplicably in the placebo phase and fell further upon active treatment. Discriminant analysis eliminated the overlap in free radical marker and selenium concentrations between control sera on the one hand and baseline or post-placebo samples from the patients on the other: antioxidant treatment normalized the relationship between these biochemical parameters. Subnormal baseline serum levels of S-adenosylmethionine drifted downwards upon active treatment whereas a sharp rise was noted when a relapse of pancreatitis occurred during the placebo phase. The results confirm that adequate exposure to antioxidants in the active treatment phase was associated with amelioration of oxidative stress, and that there was no residual effect 10 weeks after switching over to placebo treatment. Furthermore, the paradoxical behaviour of S-adenosylmethionine may imply that the beneficial effect of micronutrient antioxidants in recurrent pancreatitis is linked with preservation of the methionine trans-sulfuration pathway in pancreatic acinar cells.

Acute Disease↗
PubMed1988

Highly selective kappa opioid analgesics. Synthesis and structure-activity relationships of novel N-[(2-aminocyclohexyl)aryl]acetamide and N-[(2-aminocyclohexyl)aryloxy]acetamide derivatives.

This paper describes the synthesis, structure-activity relationships (SAR) of mu and kappa opioid binding affinities, and analgesic properties of a series of novel highly selective kappa opioid N-[(2-aminocyclohexyl)aryl]acetamide and N-[(2-aminocyclohexyl)aryloxy] acetamide derivatives. Ten compounds, 14, 15, 31-37, and 39 (Tables I and II), show a marked kappa selectivity of greater than 100:1 over mu binding, with high affinity for the kappa opioid receptor (approximately 10(-8) - 10(-9) M). Compound 39, (S,S-trans)-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-4-benzo[b] furanacetamide hydrobromide, has the highest mu/kappa selectivity, 780:1 (kappa Ki = 4.2 nM), reported to date. Four of these compounds, 14, 15, and their S,S-trans enantiomers, 37 and 39, respectively, produce effective analgesia by oral administration, as assayed by a rat-paw pressure test (RPP) (MPE50 = 24, 26, 8.3, and 12 mg/kg, respectively). The R,R-trans isomer, 38, was inactive in binding and RPP. The analgesic effect was reversed by administration of naloxone, confirming these effects are opioid in character. Optimal activity is produced when the basic nitrogen atom is in a pyrrolidine ring, the aryl group is a 10-pi-electron-rich aromatic system, such as 4-benzo[b]thiophene, 4-benzo[b]furan, or 4-chlorophenoxy, and overall lipophilicity lies within the range log P = 3.5-5.0.

Acetamides↗
PubMed1986

Klippel-Trenaunay and Sturge-Weber syndromes with renal hemangioma and double inferior vena cava.

We describe a 3 1/2-year-old boy with the Klippel-Trenaunay and Sturge-Weber syndromes. The child had congenital superficial capillary hemangiomas, congenital glaucoma and mild hydrocephalus. During the first year of life he experienced intermittent hematuria. When he was 3 years old he presented with seizures and left hemihypertrophy first was noted. Several months later radiological examination of a large abdominal mass demonstrated its origin to be in the right kidney. Radical nephrectomy documented the presence of renal hemangioma with complicating perirenal hematoma. A double inferior vena cava was another unexpected surgical finding that complicated the course of this patient. All of these unusual features in these rare syndromes with their clinical, pathogenetic and therapeutic implications are discussed. The differential diagnosis of renal masses in these syndromes also is presented.

Angiomatosis↗
PubMedDate not supplied

A double-blind placebo-controlled trial of antioxidant therapy in limited cutaneous systemic sclerosis.

OBJECTIVE: To evaluate the effects of a combination of micronutrient antioxidants (selenium, beta-carotene, vitamin C, vitamin E and methionine) with allopurinol in patients with limited cutaneous systemic sclerosis (SSc). METHODS: The study was designed as a placebo-controlled double-blind crossover study. A carryover effect was detected retrospectively for some of the prescribed antioxidants, and so the data were analysed as: (a) a between group comparison of the first 10 week treatment period; and (b) a within group comparison of the first and second 10-week periods in those who received placebo treatment first. Study end-points were plasma von Willebrand factor (vWF), thermographic response to a standard cold challenge, frequency and duration of Raynaud's attacks, patient opinion, and specialised biochemical parameters (fatty acid profiles, antioxidants and markers of free radical injury). RESULTS: Thirty-three patients were recruited. The median duration of Raynaud's phenomenon was 10 years (range 2 to 50 years) in the active-first group and 10 years (range 4 to 53 years) in the placebo-first group. In the 10-week study, there were no differences between the active and placebo groups in the change from baseline for vWF, for the parameters of the rewarming curve, or for patients' symptoms. Despite a rise in circulating antioxidant levels, there was no fall in markers of free radical mediated injury. In the 20-week cross-over study, patients did not experience any clinical benefit from active treatment compared to placebo. CONCLUSION: No clinical benefit could be demonstrated from active treatment. There are several possible explanations for this negative result, including the short duration of therapy. It is possible that antioxidant therapy, to be effective, needs to be given early in the SSc disease process, before the onset of irreversible tissue damage.

Adult↗
PubMedDate not supplied

DNA microarrays in pediatric cancer.

Childhood cancer, like all cancer, is at heart a genetic disease. Consequently, fundamental understanding of the oncogenic process is likely to be beneficially addressed by genetic methodology. Current methods have largely focused on single-gene defects, like chimeric genes, which are present in many sarcomas and leukemias. Real understanding is more likely to derive from a genome-wide analysis of these malignancies. Recent technologic advances have made it possible to simultaneously assess the entire expressed gene profile, or transcriptome, of a given cancer. Foremost among these methods is gene expression profiling using DNA microarrays. Two basic approaches predominate: spotted arrays and photolithography arrays. Regardless of the method, the resulting information can be used to create disease profiles, but only if appropriate bioinformatic solutions are employed. Common analytic approaches include two-way expression comparisons, or scatter analyses; outlier gene analysis, to identify significantly dysregulated genes; dendrogram analyses, as pioneered by Eisen; cluster analyses to identify diagnostic or biologic groups; and various forms of functional analyses to identify relevant genes and biologic pathways. Studies of both adult and pediatric cancer have demonstrated the feasibility of such analyses to identify both diagnostic and prognostic groups of tumors. Acute childhood leukemias have been grouped into myelogenous and lymphoid, and even B- and T-cell subsets. Breast cancer prognostic groups have been identified on the basis of a small subset of expressed genes. In addition, preliminary data on childhood sarcomas appear to identify both diagnostic and prognostic subsets. Specifically, embryonal rhabdomyosarcoma could be distinguished from alveolar rhabdomyosarcoma, and even morphologically mixed embryonal and alveolar rhabdomyosarcoma showed similar gene expression profiles in both histologies. Further, collaborative studies using clustering analyses appear to identify prognostic groups of diverse sarcomas. Larger institutional and cooperative group studies are currently underway to validate these preliminary findings.

Animals↗