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J Stevens

Publications and source records attributed to J Stevens.

At least 235 records · Page 13Linked to original sources
PubMed1991

Immobilized artificial membrane chromatography: rapid purification of functional membrane proteins.

A solid-phase membrane mimetic system, denoted as immobilized artificial membranes (IAM), has been developed and utilized as a novel high-performance liquid chromatography (HPLC) matrix for the first step in the rapid purification of functional membrane proteins. IAM phases consist of monolayers of amphiphilic membrane lipid molecules covalently bonded to a rigid silica particle. These monolayers of lipids have proved remarkably effective for the chromatography of biomolecules. Several cytochrome P450 isozymes, an extremely important family of hydrophobic membrane proteins with a labile heme catalytic center, have been partially purified in functional conformations from rat liver, kidney, and adrenal microsomes on IAM supports. Functionality of purified P450 and P450 reductase has been demonstrated by optical difference spectroscopy, by carbon monoxide binding, and by reconstitution of enzymatic activity in vitro. Other membrane proteins, including rat liver plasma membrane NADH oxidase and ferricyanide oxidoreductase have also been partially purified by IAM HPLC. The methods for purification of these proteins are described.

Adrenal Glands↗
PubMed1991

The ASNIS guided system for fixation of subcapital femoral fractures.

We report a prospective, consecutive series of 84 patients with 86 subcapital femoral fractures treated by internal fixation using ASNIS cannulated screws. At 1 year the clinical and radiological failure rate was 15 per cent. The failure rate was significantly influenced by age over 75 years, dementia, and fracture displacement (P less than 0.001).

Adult↗
PubMed1991

The gene encoding the oligodendrocyte-myelin glycoprotein is embedded within the neurofibromatosis type 1 gene.

In the course of efforts to identify the neurofibromatosis type 1 gene (NF1), three genes were found embedded within an intron of NF1. The cDNA sequence of one of these genes (OMGP) encodes oligodendrocyte-myelin glycoprotein. OMGP spans at least 2.7 kb of genomic DNA, and it maps within 4 kb of the breakpoint of a balanced chromosomal translocation carried by an individual with NF1. OMGP is similar in genomic structure to two other expressed genes, EVI2A and EVI2B, which lie approximately 20 and 5 kb telomeric of the OMGP locus, respectively. All three genes have the same transcriptional orientation and are contained within one intron of NF1, which is transcribed off the opposite strand. Whether altered expression of OMGP might play a role in the clinical heterogeneity of NF1 is as yet unclear.

Amino Acid Sequence↗
PubMed1991

Staffing in cardiology in the United Kingdom 1990. Sixth biennial survey: with data on facilities in cardiology in England and Wales 1989.

The Sixth Biennial Survey of Staffing in Cardiology was conducted in July 1990. This report summarises the data that were collected, together with the results of a survey of facilities in cardiology made in 1989. The total number of cardiologists in the United Kingdom, defined as individuals trained in the specialty and spending at least 40% of their time working in it, is now 323. Six individuals work part time only, making 320 whole time posts. This number has increased over the two years from 1988 to 1990 by 32, of which 23 work only in the specialty and nine as general physicians with a major interest in cardiology. The rate of increase in numbers over the past decade has been reasonably consistent with an average of approximately 4.4% per year. Thirty one districts in England and Wales still have no cardiologist and 13 other districts have little provision with an average of three (visiting) sessions each per week. The population in these 44 districts is 8.3 million. Scotland also has an inadequate distribution of service in the specialty. If recommendations for cardiac surgery and angioplasty made in the Fourth Report of a Joint Cardiology Committee of the Royal College of Physicians of London and the Royal College of Surgeons of England are to be met, we calculate that we need 63 more cardiologists in our major centres. To provide one cardiologist in every district hospital and two for larger districts would require 94 more specialists, making a total shortfall of 157 individuals. We have no excess of senior registrars to provide for a major expansion at consultant level. Time spent within the senior registrar (or academic equivalent) grade has tended steadily to decline and very few now reach the end of their contracts. The need for more individuals to pass through the senior registrar grade will be met in part by a planned reduction in the training period to three years. This will be inadequate, however, because projected retirements show that the number of consultant vacancies will increase sharply from 1997. We believe that additional senior registrar posts must be created if a serious shortfall in service provision by consultants is to be avoided. The provision of non-invasive facilities in cardiology is reasonable. The need for additional equipment for invasive cardiology has not been assessed. The number of physiological measurement technicians varies considerably between regions and is generally inadequate.

Allied Health Personnel↗
PubMed1991

DNA profiling.

Explore the source record for details and available documents.

Criminology↗
PubMed1991

Changes in body weight and girths in black and white adults studied over a 25 year interval.

Changes in body weight and shape with 25 years of aging were examined using anthropometric measurements collected in the biracial Charleston Heart Study cohort. Measurements were available from 370 men and women who were in both the 1963 and 1988 examinations. Over the 25 year interval, mean weight increased 5.4 kg in subjects who were 37-46 years of age, while mean weight decreased by 2.6 kg in 55-74 year old subjects. Nevertheless, subjects in both age categories increased in abdominal girth (10.3 cm in the younger groups vs 4.7 cm in the older subjects). There was a positive linear relationship between changes in BMI and changes in the girth measurement. With no change in body mass index (BMI), estimated increases in abdominal circumference were 2.8 cm in white women, 6.6 cm in black women, 6.3 cm in white men and 7.5 cm in black men. This longitudinal study confirms cross-sectional studies that have shown increases in trunk girth with age, and in addition shows that girths change with aging, even in the absence of changes in BMI.

Adult↗
PubMed1990

A sensitive two-site sandwich enzyme immunoassay for human angiotensin converting enzyme utilizing monoclonal antibodies.

A sensitive enzyme immunoassay was developed for human angiotensin converting enzyme. Monoclonal antibodies specific for two unique converting enzyme epitopes were utilized to develop a two-site sandwich enzyme immunoassay. Alkaline phosphatase conjugated to the detecting antibody hydrolyzes nicotinamide adenine dinucleotide phosphate (NADP) to NAD. Subsequently, NAD is cycled between its reduced and oxidized forms by an alcohol dehydrogenase/diaphorase catalyzed redox cycle. Each cycle converts iodonitrotetrazolium violet to a highly colored formazan which is quantitated. With this assay, as little as 94 pg/ml of native converting enzyme is detectable without interference from either therapeutic or endogenous converting enzyme inhibitors.

Animals↗
PubMed1990

The neurofibromatosis type 1 gene encodes a protein related to GAP.

cDNA walking and sequencing have extended the open reading frame for the neurofibromatosis type 1 gene (NF1). The new sequence now predicts 2485 amino acids of the NF1 peptide. A 360 residue region of the new peptide shows significant similarity to the known catalytic domains of both human and bovine GAP (GTPase activating protein). A much broader region, centered around this same 360 amino acid sequence, is strikingly similar to the yeast IRA1 product, which has a similar amino acid sequence and functional homology to mammalian GAP. This evidence suggests that NF1 encodes a cytoplasmic GAP-like protein that may be involved in the control of cell growth by interacting with proteins such as the RAS gene product. Mapping of the cDNA clones has confirmed that NF1 spans a t(1;17) translocation mutation and that three active genes lie within an intron of NF1, but in opposite orientation.

Amino Acid Sequence↗
PubMed1990

Deletions and a translocation interrupt a cloned gene at the neurofibromatosis type 1 locus.

Three new neurofibromatosis type 1 (NF1) mutations have been detected and characterized. Pulsed-field gel and Southern blot analyses reveal the mutations to be deletions of 190, 40, and 11 kb of DNA. The 11 kb deletion does not contain any of the previously characterized genes that lie between two NF1 translocation breakpoints, but it does include a portion of a rodent/human conserved DNA sequence previously shown to span one of the translocation breakpoints. By screening cDNA libraries with the conserved sequence, we identified a number of cDNA clones from the translocation breakpoint region (TBR), one of which hybridizes to an approximately 11 kb mRNA. The TBR gene crosses at least one of the chromosome 17 translocation breakpoints found in NF1 patients. Furthermore, the newly characterized NF1 deletions remove internal exons of the TBR gene. Although these mutations might act by compromising regulatory elements affecting some other gene, these findings strongly suggest that the TBR gene is the NF1 gene.

Adult↗
PubMed1990

A major segment of the neurofibromatosis type 1 gene: cDNA sequence, genomic structure, and point mutations.

Overlapping cDNA clones from the translocation breakpoint region (TBR) gene, recently discovered at the neurofibromatosis type 1 locus and found to be interrupted by deletions and a t(17;22) translocation, have been sequenced. A 4 kb sequence of the transcript of the TBR gene has been compared with sequences of genomic DNA, identifying a number of small exons. Identification of splice junctions and a large open reading frame indicates that the gene is oriented with its 5' end toward the centromere, in opposition to the three known active genes in the region. PCR amplification of a subset of the exons, followed by electrophoresis of denatured product on native gels, identified six variant conformers specific to NF1 patients, indicating base pair changes in the gene. Sequencing revealed that one mutant allele contains a T----C transition changing a leucine to a proline; another NF1 allele harbors a C----T transition changing an arginine to a stop codon. These results establish the TBR gene as the NF1 gene and provide a description of a major segment of the gene.

Amino Acid Sequence↗
PubMed1990

Elevation of angiotensin converting enzyme in bovine endothelial cells quantitated by an ELISA.

Levels of angiotensin converting enzyme (ACE) in cultured bovine pulmonary artery endothelial cells treated with dexamethasone, aldosterone, 3,3',5'-triiodo-L-thyronine, Ca2+ ionophore, 3-isobutyl-1-methylxanthine, dibutyryl cAMP and forskolin were quantitated by an enzyme linked immunosorbent assay (ELISA). The configuration for the ELISA consisted of purified bovine lung ACE adsorbed to a solid phase competing with endothelial cellular ACE for a limited amount of anti-ACE immunoglobulin. ACE-IgG complex on the solid phase was detected by goat anti-rabbit IgG-alkaline phosphatase conjugate with enzymatic activity measured by p-nitrophenylphosphate as substrate. This ELISA detected ACE with a sensitivity of 32 ng/ml cellular ACE. Elevation in cellular ACE catalytic activity as measured by fluorescent assay of detergent extracts from bovine endothelial cells corresponded well with an increase in ACE protein as determined by the ELISA. These results provide direct evidence that increases in catalytic activity of ACE produced in endothelial cells by a variety of agents result from enhancement of the synthesis of ACE protein.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Persistence of N-nitrosodiethanolamine contamination in American metal-working lubricants.

The potent carcinogen N-nitrosodiethanolamine (NDELA) was discovered as a contaminant of commercial metal-working lubricants over a decade ago. To determine whether or not improvements in industrial practice suggested in the meantime have eliminated this contamination from United States products, a selection of cutting fluids obtained from the current marketplace was analysed for NDELA content. All six semi-synthetic fluids examined contained NDELA at levels ranging from 0.5 to 4.3 ppm. Three of six petroleum-based lubricants and five of six synthetics also contained significant NDELA (when analysed at a detection limit of 0.03 ppm), at levels of up to 0.16 and 55 ppm, respectively. The mean concentrations were 1.5 ppm for the semi-synthetics, 0.07 ppm for the petroleum-based products, and 11.4 ppm for the synthetic metal-working fluids. While these levels are far below the values of 1-2% by weight (10,000-20,000 ppm) found in some contaminated products 13 years ago, they may nevertheless pose a continuing health risk for the machinists who work with them.

Diethylnitrosamine↗
PubMed1990

The human homolog of murine Evi-2 lies between two von Recklinghausen neurofibromatosis translocations.

Von Recklinghausen neurofibromatosis (NF1) is one of the most common inherited human disorders. The genetic locus that harbors the mutation(s) responsible for NF1 is near the centromere of chromosome 17, within band q11.2. Translocation breakpoints that have been found in this region in two patients with NF1 provide physical landmarks and suggest an approach to identifying the NF1 gene. As part of our exploration of this region, we have mapped the human homolog of a murine gene (Evi-2) implicated in myeloid tumors to a location between the two translocation breakpoints on chromosome 17. Cosmid-walk clones define a 60-kb region between the two NF1 translocation breakpoints. The probable role of Evi-2 in murine neoplastic disease and the map location of the human homolog suggest a potential role for EVI2 in NF1, but no physical rearrangements of this gene locus are apparent in 87 NF1 patients.

Animals↗
PubMed1990

Identification and characterization of transcripts from the neurofibromatosis 1 region: the sequence and genomic structure of EVI2 and mapping of other transcripts.

Mapping of the EVI2 gene between the translocation breakpoints of two patients with neurofibromatosis type 1 (NF1), combined with the likely role of its murine homolog in neoplastic disease, implicates EVI2 as a possible candidate for the NF1 gene. We report here the expression of a 1.6-kb EVI2 transcript in normal human brain and peripheral blood mononuclear cells. Sequencing studies predict an EVI2 protein of 232 amino acids that contains an N-terminal signal peptide, an extracellular domain with five potential glycosylation sites, a single hydrophobic transmembrane domain with a leucine zipper, and a hydrophilic cytoplasmic domain. These features are all well-conserved with respect to the mouse Evi-2 protein and are consistent with the hypothesis that EVI2 is a membrane protein that may complex with itself and/or other proteins within the membrane, perhaps to function as part of a cell-surface receptor. In the course of these studies we have also identified three other transcripts (classes of cDNAs) from the NF1 region. Two of these transcripts map between the NF1 translocation breakpoints; the remaining transcript maps just outside this region.

Amino Acid Sequence↗
PubMed1990

Accuracy of current, 4-year, and 28-year self-reported body weight in an elderly population.

Participants in the 1987-1989 recall of the Charleston Heart Study were asked to report their current weight and to recall their weight in 1984 and 1960. Reported weights were compared with weights measured in the respective time periods. Subjects included male and female blacks and whites between ages 62 and 100 years. Correlations between reported and measured weights over all subjects were 0.979 for current, 0.935 for 4-year, and 0.822 for 28-year recall. Subjects in the lowest body mass index quartile overestimated their weight, while subjects in the highest quartile underestimated their weight. This tendency increased as the elapsed time increased. Deviations between measured and reported weights increased as performance on cognitive tests declined.

Aged↗
PubMed1990

Prognostic factors in stage AO B-cell chronic lymphocytic leukaemia.

85 patients presenting to a single centre with stage AO B-cell chronic lymphocytic leukaemia (B-CLL) have been studied. The duration of follow-up has ranged from a minimum of 1 year to a maximum of 18 years with a mean of 6 years. 14 patients have had progressive disease and 23 patients have died, of whom nine had CLL-related deaths. We assessed the prognostic significance of the following parameters: age at presentation, sex, haemoglobin concentration, initial lymphocyte count, surface membrane phenotype, serum immunoglobulin levels at presentation and karyotype. None of these factors were predictive of survival, but there was a correlation between initial lymphocyte count, surface immunoglobulin MD lambda phenotype, and complex karyotypic abnormalities and disease progression. Two patients with a complex karyotype have been followed for more than 5 years without evidence of progression.

Adult↗
PubMed1990

Correlation of chromosome abnormalities with laboratory features and clinical course in B-cell chronic lymphocytic leukaemia.

141 patients with B-cell chronic lymphocytic leukaemia (B-CLL) have been studied for a minimum of 12 months and a maximum of 25 years. 30 of 133 patients (32.5%) had greater than 10% FMC7 positive peripheral blood lymphocytes and 19 of 131 patients (14.5%) had a serum or urinary paraprotein. At presentation 88 patients were stage A0, 18 A1, 18 A2, 11 B and six C. 44 (31%) had progressive disease and 42 (30%) died during the study period. 63 patients had a normal karyotype, 75 a clonal abnormality and in three no metaphases were obtained. The finding of a complex karyotypic abnormality was significantly associated with lambda surface phenotype (P less than 0.01), the presence of greater than 10% FMC7 positive cells (P less than 0.025), and the presence of a paraprotein (P = 0.025). Patients whose leukaemic cells had a complex karyotype and those with structural abnormalities of chromosomes 14 and 6 required treatment earlier than those with a normal karyotype.

Aged↗