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Biomedical subjects

R F Murphy

Publications and source records attributed to R F Murphy.

At least 181 records · Page 10Linked to original sources
PubMed1983

Studies on segmental pancreatic autotransplants in dogs.

Success with segmental pancreas transplants has been impaired by immunologic and technical considerations. Experiments were performed with autotransplants to avoid immunologic problems, allowing concentration on surgical techniques. Survival of splenic lobe pancreas autotransplants in pancreatectomized dogs was extended with relocation of the graft from the groin to the abdominal cavity and distal arteriovenous fistula to increase graft flow. Fibrosis of the graft occurred regardless of the method of duct treatment, latex (Neoprene) or Silastic injection or free intraperitoneal drainage. Hormonal responses in normoglycemic animals showed normal insulin levels (6 +/- 0.8 microU/mL) as compared with controls (5.4 +/- 0.9 microU/mL), while peak levels during arginine stimulation were higher in dogs with autotransplants (39.7 +/- 20 microU/mL) than in controls (15.1 +/- 1.9 microU/mL. Pancreatic polypeptide basal levels in animals with transplants were 42 +/- 2.2 pg/mL as compared with 256 +/- 28 pg/mL in controls, with no response to bombesin or protein meal stimulation. In this model, splenic lobe was capable of maintaining normoglycemia with avoidance of ketogenic amino acid patterns. Continuous fibrosis was the biggest threat to islet survival.

Amino Acids↗
PubMed1983

Reduction of the anti-metabolic and anti-proliferative effects of methotrexate by 17 beta-oestradiol in a human breast carcinoma cell line, MDA-MB-436.

We have investigated the modifying influence of 17 beta-oestradiol on the anti-metabolic and growth inhibitory actions of methotrexate (MTX) in a human breast cancer cell line, MDA-MB-436. This cell line contains detectable oestrogen receptors but is progesterone receptor-negative. Furthermore, 17 beta-oestradiol (10(-10) - 10(-6)M) failed to influence DNA synthetic rate as assessed by [3H]-TdR or [3H]-UdR incorporation and cell proliferative rate was similarly unaffected. Although by these criteria 17 beta-oestradiol failed to elicit a biological response in the MDA-MB-436 cell line, 10(-6)M 17 beta-oestradiol significantly reduced the anti-metabolic and anti-proliferative actions of MTX. In the presence of 17 beta-oestradiol approximately twice the concentration of MTX was required to inhibit cell proliferation to the same extent as was observed following exposure to MTX alone. This partial reversal of MTX effects was accompanied by a 20% reduction in the steady-state intracellular MTX concentration when cells were exposed to the drug in the presence of 10(-6)M 17 beta-oestradiol.

Breast Neoplasms↗
PubMed1983

Pharmacokinetic rationale for the interaction of 5-fluorouracil and misonidazole in humans.

As part of a Phase I clinical trial, 5 patients received 5-fluorouracil (FU) both singly and in combination with misonidazole (MISO) for the treatment of gastrointestinal cancer. Concentrations of total FU and F-containing metabolites in urine specimens, taken during 48 h after therapy, were determined. The clearance of FU following administration of 1.0 or 1.5 g FU m2 was significantly reduced by treatment with MISO (1.75-2.0 gm-2) given 2 h prior to FU therapy. Reduced clearance of FU by MISO was associated with an earlier onset of the period of nonlinearity of FU pharmacokinetics and an increased half-life of elimination. Furthermore, the clearance of FU correlated inversely with the severity of gastrointestinal toxicity. The mechanism of MISO enhancement of FU action is unlikely to be competition for microsomal enzymes, as proposed for the interaction of MISO and alkylating agents, since FU is catabolized at mitochondrial and cytosolic sites.

Adult↗
PubMed1983

Cyclic changes of plasma pancreatic polypeptide and pancreatic secretion in fasting dogs.

Fasting conscious dogs, each with a gastric fistula, Heidenhain pouch and Thomas duodenal fistula, were used. Basal pancreatic secretion showed periodic increases in phase with the periodic contraction of the stomach and duodenum. Periodic increases of plasma pancreatic polypeptide (PP), but not of gastrin, were observed in phase with the periodic contraction and secretion of the gut. Ganglion blockade abolished the cyclical activity, both secretory and motor, of the gut and of plasma PP. Intraduodenal infusion of lidocaine suppressed the spontaneous increase of pancreatic secretion and plasma PP. It is concluded both that the cyclical release of PP and the increase in pancreatic secretion are under the control of the intrinsic nerves of the duodenum.

Animals↗
PubMed1982

Kinetics of histone endocytosis in Chinese hamster ovary cells. A flow cytofluorometric analysis.

The endocytosis of histones by cultured cells was examined by flow cytofluorometry. Monolayer cultures of Chinese hamster ovary cells were incubated with fluorescein-labeled histone for various periods of time and then trypsinized to remove surface-bound protein. Internalization followed first order kinetics with a half-time of 45 min, and was linear in histone concentration up to 80 microgram/ml. Since fluorescein fluorescence decreases with decreasing pH, the fluorescence of labeled histone contained in lysosomes was expected to be decreased relative to its fluorescence at neutral pH. This was demonstrated by using chloroquine to increase the lysosomal pH of intact cells. The fluorescence of labeled histones incorporated into cells increased when those cells were incubated with 50 microM chloroquine and remeasured. This provides a method for measuring the kinetics of entry of a fluorescent probe into lysosomes. Internalization into lysosomes began almost immediately upon addition of histone, but stable nonlysosomal fluorescence appeared only after a lag of 1 h. Using suspension cultures, the short term binding and internalization kinetics were also measured. In pulse-chase experiments, lysosomal fluorescence decreased with a half-time of 30 min, but nonlysosomal fluorescence decreased with a half-time of almost 12 h, probably as a result of cell division. These results demonstrate the usefulness of flow cytometry for the quantitation and characterization of endocytosis in cultured cells.

Animals↗
PubMed1982

Flow cytofluorometric analysis of insulin binding and internalization by Swiss 3T3 cells.

The binding of a fluorescein-isothiocyanate derivative of insulin to Swiss 3T3 cells was measured by flow cytometry. The kinetics of the subsequent internalization were also measured; at a concentration of 1 microM labeled insulin approximately 25% of the internalization was insulin-specific. The kinetics of endocytosis were contrasted to those of fluorescent derivatives of histone and dextran. In addition, the fusion of endocytic vesicles containing insulin or dextran with lysosomes was detected by measuring the pH-dependent increase in fluorescein fluorescein fluorescence caused by the addition of chloroquine. The application of these results to the analysis of growth control by insulin and related hormones is discussed.

Animals↗
PubMed1982

Nonlinear pharmacokinetics for the elimination of 5-fluorouracil after intravenous administration in cancer patients.

Plasma concentrations of 5-fluorouracil (FU) and its primary catabolite, 5', 6'-dihydro-5-fluorouracil (DHFU) were measured using gas-liquid chromatography after single-dose therapy with 7.2-14.4 mg/kg. Because of the limited sensitivity of the assay for drug levels in plasma, the urinary excretion of FU and metabolites was investigated using an ion-specific electrode after either a single bolus (7.0-9.6 mg/kg) or multiple-dose therapy (6.4-7.4 mg/kg/day). Half-life values for the elimination of FU from plasma (mean, 123.5 min) were greater in each patient than for the catabolite (mean, 109.2 min). Values of the area under the curve for FU profiles varied between patients (mean +/- SE, 12.7 +/- 1.9 micrograms X h/ml) by comparison with the relatively constant values for curves of DHFU concentrations (mean +/- SE, 2.8 +/- 0.15 micrograms X h/ml). In pharmacokinetic profiles of urinary excretion a transient phase of convex shape was apparent after 80%-98% of single doses of FU was excreted. Half-lives for the elimination of FU in urine were 2.6-5.9 h, which increased to 18-44 h on multiple dosing. The results demonstrate saturation in the elimination of FU after therapeutic doses, and are consistent with the proposal that reduction of FU to DHFU provides the rate-limiting step.

Biotransformation↗
PubMed1982

The effect of parenteral and enteral nutrition on portal and systemic immunoreactivities of gastrin, glucagon and vasoactive intestinal polypeptide (VIP).

To compare the effect of parenteral with enteral nutrition on gastroentero-pancreatic hormones, hypercaloric and hypocaloric nutrient preparations, commonly used clinically, were administered to rats either through cannulae in the jugular vein or gastrostomies. Control rats were fed orally ad libitum. Portal and aortic plasma was collected for radioimmunoassay with antibodies to C-terminal regions of gastrin and glucagon and to N-terminal-to-central regions of glucagon and VIP. Levels of all immunoreactivities were significantly lower in aortic than portal plasma. Apparent clearance of glucagon and gastrin by liver or lung both was enhanced by administration of the hypercaloric nutrient intravenously. Only intragastric hypercaloric nutrition maintained levels of VIP immunoreactivity close to those of control rats. Intragastric administration of either preparation appeared to maintain adequate levels of gastrin. Differences in the levels of glucagon immunoreactivities may be related to the stimulatory effects of metabolites in the lower gut and pancreas.

Animals↗
PubMed1981

Flow cytofluorometric analysis of the nuclear division cycle of Physarum polycephalum plasmodia.

The nuclear cycle kinetics of Physarum polycephalum plasmodia were examined using flow cytofluorometry. The dyes Hoechst 33342 and propidium iodide were used to stain the DNA of isolated nuclei. In asynchronously growing microplasmodia. S phase consists of 13--15% of the nuclear division cycle time. Nuclei isolated from individual macroplasmodia, which have previously been demonstrated to divide in synchrony, were shown to be less synchronized during late S phase than during mitosis. The results obtained demonstrate the feasibility of flow cytometric measurement of the properties of nuclei isolated from a single cell.

Cell Cycle↗
PubMed1980

The native forms of the phycobilin chromophores of algal biliproteins. A clarification.

Pigments released from phycoerythrins and phycocyanins by treatment with hot methanol are currently regarded as equivalent to the native chromophores phycoerythrobilin and phycocyanobilin. However, evidence presented here confirms the original view of O'Carra & O'hEocha [(1966 Phytochemistry 5, 993-997] that these methanol-released pigments are artefacts differing in their chromophoric conjugated systems from the native protein-bound prosthetic groups. By contrast, the native spectral properties are retained in pigments released by careful acid treatment of the biliproteins and these acid-released phycobilins, rather than the methanol-released pigments, are therefore regarded as the protein-free forms of the native chromophores. The conclusion reached by Chapman, Cole & Siegelman [(1968) J. Am. Chem. Soc. 89, 3643-3645], that all the algal biliproteins contain only phycoerythrobilin and phycocyanobilin, is shown to be incorrect. The identification of a urobilinoid chromophore, phycourobilin, accompanying phycoerythrobilin in B- and R- phycoerythrins is confirmed and supported by more extensive evidence. The cryptomonad phycocyanins are shown to contain a phycobilin chromophore accompanying phycocyanobilin. This further phycobilin has the spectral properties of the class of bilins known as violins and the provisional name "cryptoviolin" is proposed pending elucidation of its structure.

Chemical Phenomena↗
PubMed1980

Structures and apoprotein linkages of phycoerythrobilin and phycocyanobilin.

Phycoerythrobilin and phycocyanobilin are covalently attached to the apoproteins of phycoerythrins and phycocyanins. One linkage consists of an ester bond between the hydroxy group of a serine residue and the propionate side chain on one of the inner pyrrole rings (probably ring C). The other linkage is a labile thioether bond between a cysteine residue and the two-carbon side chain on pyrrole ring A. This side chain and both of the alpha-positions of the ring A are in the reduced state. This constitutes an important structural revision, since, in the structures currently accepted for the phycobilins, the two-carbon side chain on ring A is depicted as an ethylidene grouping and this has been regarded not only as a very characteristic feature of the phycobilins, but also as a probable structural feature of the chromophore of phytochrome, largely on the basis of other analogies with the phycobilins. The ethylidene-containing structures apply instead to artefact forms of the pigments released from the apoproteins by treatment with hot methanol. Cleavage of the ring-A linkage involves an elimination reaction releasing the cysteine residue and generating a double bond in the ring-A side chain. During cleavage in methanol the direction of the elimination is towards the ring, generating the ethylidene double bond. Since this is linked to the conjugated system, the methanol-released pigments differ spectrally from the native phycobilins. During acid-catalysed release of the pigments, the elimination apparently goes in the opposite direction, generating a double bond at the outer position of the side chain. Since this double bond is not linked to the conjugated system, the acid-released pigments remain spectrally identical with their protein-bound counterparts.

Amino Acids↗