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Biomedical subjects

R J Maxwell

Publications and source records attributed to R J Maxwell.

At least 91 records · Page 5Linked to original sources
PubMed1988

Vasoactive intestinal peptide stimulates glycolysis in pituitary tumours; 1H-NMR detection of lactate in vivo.

1H- and 31P-NMR spectroscopy has been applied to rats carrying implanted tumours in vivo, and used to observe simultaneous changes in intracellular pH (pHi) and lactate concentration during the stimulatory action of vasoactive intestinal polypeptide (VIP). A maximal decrease in pHi to a mean of 0.29 units below basal values was recorded. At the same time, 11 min after VIP, a maximal increase in tumour lactate was found, with a mean value of 150% of the basal concentration. The magnitude of these changes was compatible with in vitro measurements of basal lactate concentration and buffering capacity made on the same tumour line. It is concluded that VIP stimulates glycolysis by the tumour cells, resulting in an accumulation of lactate and a consequent fall in pHi.

Adenoma↗
PubMed1987

Hepatic fatty acid profiles in aflatoxin-exposed broiler chickens.

This study was initiated to determine whether a specific fatty acid marker from hepatic lipids could be identified to confirm aflatoxin exposure in chickens. Male broiler chicks (240) were reared to 21 days of age on diets containing 0, 625, 1.25, 5.0, and 10.0 ppm aflatoxin. Live weights and organ weights differed significantly among the dietary groups. Total liver lipids increased significantly (P less than .001) with increasing aflatoxin levels. Separation of extracted lipids into neutral and polar fractions established that this increase in hepatic lipid was accounted for almost entirely by increases in neutral lipid fractions. A gain of 117% occurred in the weight of neutral lipids as aflatoxin increased from 0 to 10 ppm. In both neutral and polar lipid fractions subsequent chromatographic analysis of fatty acid methyl esters (FAME) showed linear increases in the monoenoic fatty acids with increasing aflatoxin. No single FAME from either lipid fraction was suitable for confirming aflatoxin exposure.

Aflatoxins↗
PubMed1987

Construction of expression vectors for the production of interferons in yeast.

Expression vectors designed for the production of foreign proteins in yeast are constructed as a composite of functional DNA segments brought together in a single plasmid DNA molecule. Such a composite DNA molecule constitutes a complex entity in terms of its replication and selection functions (in both E. coli and S. cerevisiae) and its gene expression properties. The latter depend critically upon transcriptional control signals (the promoter and terminator regions from a highly expressed yeast gene) that are used to direct the expression of foreign genes in yeast cells. This paper describes the construction of such an expression vector based on the transcription control signals of the yeast phosphoglycerate kinase gene and its application to the production of human interferon-alpha's in yeast cells.

Cloning, Molecular↗
PubMed1987

Effects of pulmonary embolism on survival of patients with Greenfield vena caval filters.

The late mortality in 167 patients who had Greenfield vena caval filters inserted after episodes of acute pulmonary embolism is reported. The mean follow-up period of the survivors was 42 months; the mean survival time of the 48% who died was 9.3 months. The mortality rate in 50 comparable patients who did not have pulmonary embolism but had prophylactic filter insertion was 52% with a mean survival time of 9.4 months. The mean follow-up period of the survivors was 28 months. Age, mean pulmonary artery pressure, and severity of the initial embolic episode did not predict the increased rate of late mortality. We conclude that for patients who survive acute pulmonary embolism and have treatment to prevent recurrence, the embolic history of thromboembolism has little impact on late mortality, which is determined by their preexisting serious medical conditions.

Adolescent↗
PubMed1986

The nucleotide sequence of the mitochondrial DNA genome of an abundant petite mutant of Saccharomyces cerevisiae carrying the ori1 replication origin.

We have determined the 903 bp nucleotide sequence of the mitochondrial DNA genome of a Saccharomyces cerevisiae petite mutant BB5. This petite, containing the 265 nucleotide ori1 region, is representative of a class of petites arising at exceptionally high frequency within the population of spontaneous petites derived from a particular mit- strain Mb12. The DNA sequences of both the ori1 region and the flanking intergenic regions have been compared to those of the corresponding regions of mtDNA in a previously reported petite strain, a1/1R/1 of Bernardi's laboratory, that has a similar (880 bp) repeat unit. The BB5 petite genome carries a canonical ori1 sequence that is identical in both petite mtDNAs, but the flanking intergenic sequences show significant differences between the two petite strains. The divergence is considered to arise from differences in the sequences flanking ori1 in the respective parent strains.

Base Sequence↗
PubMed1986

Motilin's induction of phasic contractility in canine jejunum is mediated by the luminal release of serotonin.

To determine whether mucosal serotonin (5-HT) is involved in the intestinal motility response to motilin, we studied the effects of intra-arterial infusions of motilin (5 X 10(-10) mol/L) in isolated, vascularly perfused segments of canine jejunum. Intraluminal pressures were continuously recorded through a perfused manometric catheter, and venous and luminal 5-HT levels were measured by radioimmunoassay. Luminal 5-HT output rose from a basal of 54 +/- 12 to a peak of 151 +/- 30 ng/min X 100 gm (p less than 0.01) with the motilin infusion. The earliest significant rise in luminal (5-HT), which occurred at 1 minute after the start of the motilin infusion, preceded the onset of phasic contractility. The rise in the motility index induced by motilin demonstrated a strong correlation (r = 0.72, p less than 0.01) with rises in luminal 5-HT output. 5-HT tachyphylaxis abolished the motility response to motilin; prior treatment with atropine abolished, while tetrodotoxin inhibited the luminal release of 5-HT. An infusion of exogenous 5-HT giving equivalent luminal 5-HT levels as induced by motilin led to similar phasic contractility and rise in the motility index. These findings suggest that motilin initiates phasic contractility in canine jejunum through the cholinergically mediated release of mucosal serotonin.

Animals↗
PubMed1985

Solitary squamous papilloma of the bronchus.

A case of solitary squamous papilloma of the bronchus is described and 11 other cases from the reports published worldwide are reviewed. These tumours present in middle aged men with symptoms similar to those of bronchial carcinoma. Treatment by bronchoscopic removal or lobectomy is usually curative. Symptoms are similar to those of bronchial carcinoma, but a correct preoperative diagnosis permits more conservative surgery to be carried out. Difficulties in the histological classification of papillary tumours of the bronchus are discussed.

Aged↗
PubMed1983

Biogenesis of mitochondria: the mitochondrial gene (aap1) coding for mitochondrial ATPase subunit 8 in Saccharomyces cerevisiae.

A mitochondrial gene (denoted aap1) in Saccharomyces cerevisiae has been characterized by nucleotide sequence analysis of a region of mtDNA between the oxi3 and oli2 genes. The reading frame of the aap1 gene specifies a hydrophobic polypeptide containing 48 amino acids. The functional nature of this reading frame was established by sequence analysis of a series of mit- mutants and revertants. Evidence is presented that the aap1 gene codes for a mitochondrially synthesized polypeptide associated with the mitochondrial ATPase complex. This polypeptide (denoted subunit 8) is a proteolipid whose size has been previously assumed to be 10 kilodaltons based on its mobility on SDS-polyacrylamide gels, but the sequence of the aap1 gene predicts a molecular weight of 5,815 for this protein.

Adenosine Triphosphatases↗
PubMed1983

Systematic protocol for the accumulation of fatty acid data from multiple tissue samples: tissue handling, lipid extraction and class separation, and capillary gas chromatographic analysis.

A systematic procedure was developed for detailed fatty acid profiling of both neutral and polar lipid fractions isolated from hundreds of related bovine muscle and adipose tissue samples. A regimen was established for a nonbiased handling of tissue samples, which included their handling in a predetermined random order. Lipid class separation was accomplished concomitantly during the extraction of the tissues by a selective dry column method, which allowed a detailed analysis of minor but important polyunsaturated fatty acids associated with the polar fraction. Neutral lipids were derivatized to fatty acid methyl esters (FAME) by a literature procedure. However, to protect against lysis of plasmalogens in the polar fraction, a modified nonacidic esterification procedure was developed. FAME profiles were obtained on a programmable high resolution capillary gas chromatograph (GC). Run programs for unattended GC operation and data storage are described. By this overall procedure, the quantitation and peak identification were obtained for major and minor fatty acid constituents from bovine tissue in a manner that prepares for valid statistical interpretation of the resulting data.

Adipose Tissue↗
PubMed1983

Systematic management and analysis of fatty acid data from multiple tissue samples.

A systematic approach has been developed for the collection and analysis of gas chromatographic (GC) data from multiple fatty acid profiles. The approach was applied to a series of polar and nonpolar tissue lipids generated in animal feeding studies to allow a comparison of mean fatty acid profiles as a function of either dietary regimen or tissue location. The magnitude of the studies, sufficiently large to minimize error from animal variabilities, mandated the use of computer assistance. Nevertheless, manual input was essential due to the complexity of the GC patterns, and was invoked for peak assignment and report editing. The approach discussed here allowed for the consolidation and statistical analysis of data from over 30,000 GC peaks, and generated results in both tabular and graphic formats. It should be extendable to other chromatographic studies of lipid components.

Adipose Tissue↗
PubMed1982

Amino acid composition of gliadin fractions which may be toxic to individuals with coeliac disease.

Fraction 9, prepared by chromatography of a peptic-tryptic-pancreatinic digest of gliadin on S.P. Sephadex C-25, was re-chromatographed on Q.A.E. Sephadex A-25 and subfractions 9-1 and 9-2 further purified on S.P. Sephadex C-25. Sub-fractions 9-1 and 9-2 and the purified sub-fractions 9-1B and 9-2B appeared to be toxic to patients with coeliac disease on the basis of causing a reduction in D-xylose absorption. Amino acid analysis of undigested residues from sub-fractions 9-1B and 9-2B obtained after 'in vitro' digestion with remission coeliac mucosa contained mainly glutamine/glutamic acid and proline with some serine, leucine, phenylalanine and glycine. Another fraction (fraction 3) of wheat gliadin prepared by peptic-tryptic digestion and ion-exchange chromatography on S.P. Sephadex, previously shown to produce a skin-reaction in adults with coeliac disease, has been further purified by ion exchange chromatography, isoelectric focusing and gel filtration. The sub-fractions were submitted to amino acid analysis and the results compared with those from the undigested residues above. Isoelectric focusing of fraction 3 of the P.T. digest and its sub-fractions showed the presence of peptides of pI approximately 4.8 and 5.6 with only small amounts of peptides on either side of this region. Mucosal digestion of fractions of peptic-tryptic-pancreatinic gliadin digests 'in vitro' appears to be a promising method for the elucidation of the primary structure of that section of the gliadin which may be responsible for the lesion in coeliac disease. The evaluation of higher molecular mass peptic-tryptic digests by intradermal skin tests could also be useful for the preliminary screening of fractions for feeding tests, but this approach seems less likely to indicate the toxic region of the gliadin molecule.

Adult↗