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Biomedical subjects

R F Murphy

Publications and source records attributed to R F Murphy.

At least 199 records · Page 11Linked to original sources
PubMed1980

Rapid plasma clearance and reduced rate and extent of urinary elimination of parenterally administered methotrexate as a result of severe vomiting and diarrhoea.

A patient received 200 mg methotrexate IM as part of a treatment schedule for malignant melanoma. Severe vomiting and diarrhoea began shortly after treatment and persisted for 4 h. During this period the methotrexate renal clearance rate was 37 ml . min-1, increasing to 97 ml . min-1 when vomiting and diarrhoea ceased. Only 26% of the administered dose was recovered in the urine up to 48 h after treatment, whilst the plasma clearance of methotrexate assessed over the same period was 208 ml . min-1. We conclude that a considerable proportion of the dose was lost from the gastrointestinal tract during the period of vomiting and diarrhoea, and that consequently enterohepatic circulation of methotrexate plays an important role in the pharmacokinetics of the drug.

Diarrhea↗
PubMed1980

Isolation of newly replicated chromatin by using shallow metrizamide gradients.

The properties of chromatin containing newly synthesized DNA and protein were investigated. A fraction of chromatin enriched in newly replicated DNA was isolated by means of its increased density in metrizamide relative to bulk chromatin. The DNA of this fraction appeared to be packaged into nucleosomes but at a reduced nucleosomal spacing. Although pulse-labeled DNA was present in this dense fraction, nucleosomes labeled with short pulses of arginine or acetate were of normal density. The data presented are consistent with the conclusion that newly replicated DNA is associated with preexisting histones in a short-lived, compact structure whereas newly synthesized histones are deposited at normal spacing some distance from the replication fork.

Animals↗
PubMed1979

Computer programs for analysis of nucleic acid hybridization, thermal denaturation, and gel electrophoresis data.

Computer programs for the analysis of data from techniques frequently used in nucleic acids research are described. In addition to calculating non-linear, least-squares solutions to equations describing these systems, the programs allow for data editing, normalization, plotting and storage, and are flexible and simple to use. Typical applications of the programs are described.

Computers↗
PubMed1979

Hybridization of synthetic oligodeoxyribonucleotides to phi chi 174 DNA: the effect of single base pair mismatch.

Oligodeoxyribonucleotides complementary to the DNA of the wild type (wt) bacteriophage phi chi 174 have been synthesized by the phosphotriester method. The oligomers, 11, 14, and 17 bases long, are complementary to the region of the DNA which accounts for the am-3 point mutation. When hybridized to am-3 DNA, the oligonucleotides form duplexes with a single base pair mismatch. The thermal stability of the duplexes formed between wt and am-3 DNAs has been measured. The am-3 DNA:oligomer duplexes dissociate at a temperature about 10 degrees C lower than the corresponding wt DNA:oligomer duplexes. This dramatic decrease in thermal stability due to a single mismatch makes it possible to eliminate the formation of the mismatched duplexes by the appropriate choice of hybridization temperature. These results are discussed with respect to the use of oligonucleotides as probes for the isolation of specific cloned DNA sequences.

Bacteriophage phi X 174↗
PubMed1979

Physicochemical and biological properties of glucagon-like polypeptides from porcine colon.

Polypeptide material displaying glucagon-like immunoreactivity was isolated from porcine colon using immunoaffinity chromatography. The immunoreactive material was tightly bound to high molecular weight proteins but was dissociated by 0.1% w/v sodium dodecyl sulphate solution into immunoreactive components of approximate molecular weights 12,000,8000,5000 and 3000. These components reacted at least 50 times more strongly with antibodies specific for the N-terminal region of glucagon than with antibodies specific for the C-terminal region of glucagon. While the 8000 and 3000 dalton fractions were homogeneous, the 12,000 and 5000 dalton fractions were resolved into multiple bands by isoelectric focusing. The 12,000 dalton fraction was devoid of glycogenolytic and lipolytic activity, was not insulin releasing and showed no ability to bind to receptor sites specific for glucagon on hepatic plasma membranes and to active hepatic adenylate cyclase. The 8000 and 5000 dalton components showed weak lipolytic activity. The possible significance of colonic glucagon-like immunoreactivity relative to pancreatic glucagon and immunoreactivity from other tissues is discussed.

Adenylyl Cyclases↗
PubMed1979

Starvation-induced changes in secretin-like immunoreactivity of human plasma.

Levels of secretin-like immunoreactivity in the plasma of 50 starved subjects were measured by radioimmunoassay and rose from 18 +/- 3 (S.E.) pg/ml after 12 h, to 103 +/- 12 pg/ml (P less than 0.005) after 36 h. The assay antibodies were found to be specific for a region of secretin located towards the C-terminal residue. Lactoperoxidase was used to label the secretin with 125I and ionexchange chromatography on SP-Sephadex C-25 was used to purify the labelled product. The plasma immunoreactivity was purified by immunoaffinity chromatography on antibody-Sepharose conjugates and characterised by gel-filtration on Sephadex G-50 calibrated with molecular weight markers. After a 12-h fast, 10-20% of the immunoreactivity had a molecular weight of about 12 000, possibly due to precursors of secretin. Most of the remainder was smaller than secretin with molecular weight of less than 3000. This material comprised over 90% of the plasma immunoreactivity after a 36-h fast and may be due to degradation products.

Antibody Specificity↗
PubMed1979

The use of perfused rat intestine to characterise the glucagon-like immunoreactivity released into serosal secretions following stimulation by glucose.

Isolated perfused intestine of rat was used to demonstrate the glucose-stimulated release of glucagon-like immunoreactivity (GLI) into serosal secretions. The released GLI was characterised using immunoaffinity chromatography on columns of immobilised antibodies specific for the N (residues 1 to 18) and for the C (residues 19-29) terminal portions of glucagon followed by gel-filtration. The immunoreactivity was present in a variety of molecular species. These include a large GLI which has a molecular weight about 12000 and binds to antibodies specific for the N-terminal portion of glucagon and two polypeptide fractions with molecular weight closer to that of glucagon. While one fraction of the small GLI boun both to antibodies specific for the C-terminal and N-terminal portions of glucagon the other bound only to the former antibodies. The relevance of these findings to the origins of circulating GLI and the possible precursor relationship between large and other forms of GLI is discussed.

Animals↗
PubMed1978

Altered nucleosome spacing in newly replicated chromatin from Friend leukemia cells.

Chromatin from Friend leukemia cells labeled with [14C]thymidine for 24 hr followed by [3H]thymidine for 10 min is converted into nucleosomes by staphylococcal nuclease at only half the rate that total chromatin is converted. Polyacrylamide gel electrophoresis of nucleosomal DNA from cells labeled for 24 hr with [14C]thymidine followed by 10 min with [3H]thymidine demonstrates that the internucleosomal spacer of newly replicated chromatin is approximately 20 base pairs shorter than that of total chromatin. The implications of this difference for models of chromatin structure are discussed.

Animals↗