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Biomedical subjects

R Stephens

Publications and source records attributed to R Stephens.

At least 37 records · Page 2Linked to original sources
PubMed1995

Case report: congenital adrenal hyperplasia and malignant Leydig cell tumor.

Leydig cell tumors are very rarely seen testicular tumors and can be difficult to distinguish from testicular tumors of the adrenogenital syndrome. Testicular tumors of the adrenogenital syndrome are confined to patients with congenital adrenal hyperplasia. The authors report a case of a patient with malignant Leydig cell tumor and a history of congenital adrenal hyperplasia (adrenogenital syndrome). To the authors' knowledge, this has not been reported previously.

Adrenal Hyperplasia, Congenital↗
PubMed1995

Workshop on perinatal exposure to dioxin-like compounds. I. Summary.

An international workshop reviewed 20 ongoing or recently completed studies of the effects of perinatal exposures to dioxins, dibenzofurans, and PCBs on the reproductive, endocrine, neurodevelopmental, and immune systems. Many of the observed effects are consistent with these compounds acting as "environmental hormones" or endocrine disrupters. This report summarizes the conclusions and future directions described at the workshop.

Animals↗
PubMed1994

Equine infectious anemia virus trans-regulatory protein Rev controls viral mRNA stability, accumulation, and alternative splicing.

The cis- and trans-acting components of the Rev regulatory pathway employed by equine infectious anemia virus (EIAV) to regulate and coordinate viral gene expression were examined in complementation experiments. Viral protein expression and mRNA expression were compared in cells transiently transfected with wild-type or mutant proviruses in combination with Rev expression plasmids. Mutation of the predicted rev gene abolished Gag protein synthesis, and this defect was complemented, in trans, by Rev. Analysis of viral mRNAs from transfected cells confirmed that EIAV expresses five major mRNAs: the full-length and singly spliced mRNAs contain introns and encode viral structural proteins while the three fully spliced mRNAs, encoding nonstructural genes, are generated by alternative splicing. Compared to cells transfected with the wild-type provirus, the intron-containing mRNAs produced from the rev-minus mutant were present at reduced levels in the nuclear RNA fraction and were not detected in the cytoplasm. This pattern of viral mRNA synthesis was restored to the wild-type pattern by providing Rev in trans. In contrast to the intron-containing mRNAs, cytoplasmic accumulation of the multiply spliced class of mRNAs was independent of Rev. Closer examination of the multiply spliced class of viral mRNAs by reverse transcriptase-PCR analysis revealed a Rev-dependent alternative splicing phenomenon. In the absence of Rev, proviruses expressed a four-exon mRNA at high levels; the addition of Rev caused both a decrease in the levels of the four-exon mRNA and the appearance of a related mRNA lacking exon 3. The cis-acting RNA elements that mediate Rev responsiveness were studied with deleted proviruses, which revealed that EIAV contains at least two elements located near the ends of envelope gene. Unlike the Rev-responsive elements in other retroviruses, the cis-acting regions of EIAV do not appear to form complex secondary structures.

Alternative Splicing↗
PubMed1993

Abundant urokinase activity on the surface of mononuclear cells from blood and bone marrow of acute leukemia patients.

We have examined the mononuclear cell fraction from 35 individuals, 18 with hematologic malignancies and 17 healthy controls for the presence of cell surface-associated plasminogen activator (PA) activity. PA activity was found on the cell surface of 10 out of 12 samples from patients with acute leukemia. In addition to active urokinase (uPA) found on the cell surface in four out of five acute myeloid leukemia patients, tissue-type PA activity was detected in the same samples (3 of 5). Two out of four samples from acute lymphoid leukemia displayed only uPA activity and three out of three samples from biphenotypic leukemia were also clearly uPA-positive. Plasmin activity was not detected in any of the samples. PA activity was not found on the surface of mononuclear cells from either patients with chronic lymphoid leukemia or healthy controls and, in this respect, the cell surface-bound uPA activity behaved as a marker for acute leukemia. The finding of PA activity on the cell surface in acute leukemia suggests that there may be continuous generation of plasmin with consequent consumption of plasma plasmin inhibitors.

Bone Marrow↗
PubMed1993

Acidic hydrolysis of plasmalogens followed by high-performance liquid chromatography.

A simple, quantitative method for determining the plasmalogen content of small samples is reported here. The method uses the different susceptibility to acid-catalyzed hydrolysis of the alkyl, alkenyl and acyl linkages to separate the plasmalogen subclass from the other two non-labile subclasses. Hydrolysis of plasmenylethanolamine and plasmenylcholine was complete after 4 and 1 min of acid treatment, respectively. The acid-catalyzed hydrolysis did not alter the phospholipid fatty acid composition, making this method useful for fatty acid compositional analysis of the plasmalogen subclass. High-performance liquid chromatography was used for separations, and phospholipids were quantitated by assay of lipid phosphorus or by direct quantitation of peak area. Using this method, small amounts (10 nmol) of ethanolamine glycerophospholipid and choline glycerophospholipid are subjected to acid-catalyzed hydrolysis and subsequent separation of the resulting lysocompounds obtained from plasmalogens from the more acid-stable alkylacyl and diacyl glycerophospholipid fractions. Our values for plasmalogens from commercial preparations of choline and ethanolamine glycerophospholipids agree with literature values. The usefulness of the method is demonstrated for small glycerophospholipid samples that are equivalent to samples from cultured neural cells.

Acids↗
PubMed1993

Overexpression of Her-2/neu may be an indicator of poor prognosis in prostate cancer.

Previous reports have shown that Her-2/neu oncogene expression in human breast cancer and ovarian cancer may be associated with poorer prognosis. We report the expression of Her-2/neu on fresh samples of known prostatic adenocarcinoma but not on those of benign prostatic hypertrophy. Using a monoclonal antibody (TA1) directed against human Her-2/neu oncogene product and an immunohistochemical staining method, no Her-2/neu expression was noted with benign prostatic hypertrophy (15 samples). With prostatic adenocarcinoma samples, a subset (9 of 25) showed overexpression of Her-2/neu. Such overexpression is correlated with higher histological grade, higher stage of disease, and high S phase and aneuploidy on flow cytometric analysis. These findings suggest that Her-2/neu may be a prognostic marker in prostate cancer as well.

Adenocarcinoma↗
PubMed1993

The impact of clinical trials on the treatment of lung cancer.

A large number of clinical trials have been conducted in lung cancer, but very few surveys have attempted to assess their impact on actual clinical practice. A questionnaire was therefore designed to address this question, and, in addition, to collect information on the numbers of patients referred and entered into trials by radiotherapists and medical oncologists in 1991. The questionnaire was sent to all 295 radiotherapists and medical oncologists in the UK, and the response rate was 81%. The respondents had 12,640 lung cancer patients referred to them and entered 2352 of them into trials. These numbers indicate that only 40% of all lung cancer patients are referred to a radiotherapist or medical oncologist, and suggest that, overall, fewer than 5% are entered into trials. Large multicentre randomized clinical trials were widely quoted as having an impact, and participants in trials were more likely to adopt trial results into their practice.

Clinical Trials as Topic↗
PubMed1993

A simulated sequential analysis based on data from two MRC trials.

The motivation for proposing sequential methods for cancer clinical trials is presented, and the methodology examined by re-analysing two completed phase III cancer trials of the Lung Cancer Working Party of the British Medical Research Council. The reanalysis proceeds as if the trials had been designed with a planned series of interim analyses governing stopping. Specifically, the triangular and double-triangular tests were applied. The sequential reanalysis gave a substantial reduction in the number of patient required, and deaths observed, for conclusions to be reached in comparison with the completed studies. In each case, the sequential analysis was stratified for baseline prognostic factors which were seen to be important at the first interim analysis.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Enzyme immunoassay for detection of human immunodeficiency virus-specific immunoglobulin A antibodies.

Early diagnosis of human immunodeficiency virus (HIV) infection may be difficult in adults with acute or recent HIV infection and in infants with perinatally acquired HIV. Detection of HIV-specific immunoglobulin A (IgA) antibodies in infant serum by Western blot (immunoblot) has been suggested as a reliable method to identify HIV-infected infants, especially those over the age of 6 months, and as an adjunct to diagnosis of acute HIV infection in adults. We developed a simple enzyme immunoassay for detection of HIV-specific IgA, using standard commercially available reagents. Enzyme immunoassay was comparable to Western blot for detection of HIV-specific IgA in sera from adults (n = 216), older children (n = 49), and infants born to HIV-infected mothers (n = 65). Specificity was 100% and sensitivity ranged from 80 to 92%. IgA-enzyme immunoassay is a simple, highly sensitive method for detection of HIV-specific IgA antibodies and is easily adapted to the standard clinical laboratory.

Adolescent↗