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Biomedical subjects

C Robinson

Publications and source records attributed to C Robinson.

At least 415 records · Page 23Linked to original sources
PubMed1984

Anaphylactic- and calcium-dependent generation of prostaglandin D2 (PGD2), thromboxane B2, and other cyclooxygenase products of arachidonic acid by dispersed human lung cells and relationship to histamine release.

Proteolytic digestion of human lung tissue dispersed a population of cells (HDLC) containing 1 to 8% mast cells but which were free from bronchial and vascular smooth muscle. Incubation of HDLC with anti-human IgE, which released a net 24.8 + 4.3% of mast cell-derived histamine, stimulated a 14-fold increase in the generation of PGD2, a seven-fold increase in TXB2, and less than a twofold increase in PGF2 alpha, immunoreactive PGE, (i-PGE) and 6-keto-PGF1 alpha. A similar profile of prostanoid release was observed when cells were challenged with epsilon-specific anti-IgE, indicating that the response was specific to the coupling of IgE Fc receptors. The calcium ionophore A23187 also released prostanoids from HDLC in approximately the same proportions as anti-IgE. This stimulus, however, released only 50% as much PGD2 per nanogram histamine than did IgE-dependent activation, thereby showing a fundamental difference in the mechanisms by which the two agents activate mast cells and liberate arachidonic acid for oxidative metabolism. In concentration-response and time course experiments, both secretory stimuli released prostanoids and histamine in parallel. After separation of lung cells by isopyknic centrifugation, challenge with anti-IgE or A23187 released PGD2 only from those fractions containing mast cells, the amount released corresponding closely to both the mast cell concentration and net histamine release. On pooling data from all experiments, the closest correlation was found between release of PGD2 and histamine when cells were stimulated with either anti-IgE (r = 0.813, p less than 0.001) or A23187 (r = 0.763, p less than 0.001), supporting a mast cell origin for PGD2. The release of other prostanoids in fractions not containing mast cells demonstrates that macrophages, monocytes, and lymphocytes have the capacity to generate TXB2, PGF2 alpha, and i-PGE both in the absence and presence of mast cells. Thus, although mast cells are likely to be the major source of PGD2 generated upon IgE-dependent stimulation of HDLC, other cells dispersed from lung tissue have the capacity to generate prostanoids directly after activation of their IgE-Fc receptors and, indirectly after the secretion of mast cell mediators.

Anaphylaxis↗
PubMed1984

Noninvasive testing of the carotid system.

Noninvasive diagnostic techniques have a high degree of accuracy in identifying hemodynamically significant narrowing of the extracranial carotid artery. Ocular pneumoplethysmography, periorbital Doppler ultrasonography and cerebrovascular thermography focus on the ophthalmic artery and its branches as well as terminal branches of the external carotid artery. Carotid phonoangiography and ultrasonic Doppler arteriography focus directly on the cervical carotid complex.

Carotid Arteries↗
PubMed1983

Thromboxane A2 analogues inhibit the metabolism of thromboxane B2 in perfused guinea-pig lung.

The effect of four thromboxane A2-like analogues as inhibitors of thromboxane B2 uptake and metabolism to 13,14-dihydro-15-keto-thromboxane B2 was studied in the perfused guinea-pig lung. We used 5-min infusions containing 1 muCi [3H]thromboxane B2 (10 ng/ml) and measured uptake/accumulation (as tissue to medium ratio) and metabolism to 13,14-dihydro-15-ketothromboxane B2 by radio-TLC. The results showed that thromboxane B2 metabolism is saturable and exhibits substantial dose-dependent inhibition of both processes by U46619 and U44069 endoperoxide analogues (50% inhibition, ID50, in the range 0.5-0.9 microM), pinane thromboxane A2 (a thromboxane A2 partial agonist, ID50 against metabolism, 0.7 microM) and the thromboxane A2 mimetic EPO11 (ID50 against metabolism, 2.6 microM). These agents affected uptake and enzyme transformation steps differentially, thus strengthening the evidence that thromboxane B2 metabolism is a multi-step, uptake-dependent process in this tissue. U46619 did not affect prostaglandin F2 alpha metabolism, nor did prostaglandin F2 alpha inhibit thromboxane B2 metabolism, confirming that thromboxane B2 uptake/metabolism is distinct from the process which handles prostaglandins. Of the four analogues, only pinane thromboxane was a significant substrate for 15-hydroxyprostaglandin dehydrogenase and it was also the best inhibitor of 15-hydroxyprostaglandin dehydrogenase in purified enzyme preparations. These results advance our understanding of the inactivation in lung of thromboxane B2 and invite study of thromboxane A2 itself.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1983

Secretory carcinoma of the breast in adults. Light and electron microscopic study of three cases with review of the literature.

Three adult cases of secretory carcinoma of the breast were studied by both light and electron microscopy. Histologically the tumors revealed three patterns, namely, solid, microcystic and ductal. Ultrastructurally the tumor cells contained large numbers of membrane-bound intracytoplasmic secretory vacuoles. In addition, numerous intracytoplasmic as well as intercellular lumina containing abundant secretory material were noted. Secretory carcinoma in adults is rare with only twenty cases reported previously in the literature. It is known to have a better prognosis than the usual ductal carcinoma. The most appropriate treatment appears to be an extended simple mastectomy.

Adult↗
PubMed1983

Changes in the protein components of rat incisor enamel during tooth development.

Enamel-matrix components from rat incisor enamel were extracted from tissue at different stages of development on single teeth. Separations of proteins using urea and SDS acrylamide gel electrophoresis were compared. The bulk of the matrix exhibited SDS mol. wt of 25-30,000 with smaller amounts at approximately 18,000 and about 10-12,000. Trace amounts of material at -50,000 and 70,000 were detected. These were presumably associated with the mineral phase as their yield increased after demineralization. The proportion of small molecular weight components increased with tissue age. Using urea, many more proteins were separated (up to 20) into fast, intermediate and slowly-migrating components. Disappearance of small bands of intermediate mobility at the end of matrix secretion suggested that they were early ameloblast products which were rapidly degraded after secretion. Both slowly- and rapidly-migrating components increased with tissue age indicating progressive degradation of parent molecules of intermediate mobility into highly charged and relatively uncharged molecules.

Animals↗
PubMed1983

Correction of a genetically caused enzyme defect by somatic cell hybridization.

Liver cells obtained from newborn mice homozygous for any one of several overlapping deletions in chromosome 7 fail to express a number of liver-specific differentiated traits. Among these is the activity of the membrane-bound liver-specific enzyme glucose-6-phosphatase (Glc-6-Pase; D-glucose-6-phosphate phosphohydrolase, EC 3.1.3.9). Previous studies have led to the suggestion that the region of the genome covered by these deletions includes genes that normally regulate the expression of structural genes encoding liver-specific enzymes and proteins mapping elsewhere in the genome. To find out whether the deficiency of Glc-6-Pase may be caused by the deletion of the relevant structural gene, mouse liver cells homozygous for the deletion c14CoS were hybridized with 2S Faza rat hepatoma cells, and the hybrid cell cultures were analyzed for mouse and rat Glc-6-Pase activity. Hybrids showed expression of mouse Glc-6-Pase activity, proving that the structural gene for this enzyme is not included in the deletion c14CoS in chromosome 7. In the hybrid cells the rat hepatoma genome apparently contributes a factor that activates the structural gene of the mouse and corrects its failure of expression, which most likely resulted from the deletion of an essential regulatory or processing gene. By using as a marker glucose-6-phosphate isomerase (Glc-6-PIase; glucosephosphate isomerase, D-glucose-6-phosphate ketolisomerase, EC 5.3.1.9), known to map on chromosome 7, this entire chromosome could be excluded as a possible carrier of the Glc-6-Pase structural gene. In addition, the structural genes for Glc-6-Pase and for tyrosine aminotransferase (TyrATase; L-tyrosine:2-oxoglutarate aminotransferase, EC 2.6.1.5), another enzyme deficient in lethal deletion homozygotes, were shown to map on two different chromosomes. Together with our previous studies of TyrATase gene regulation, the present experiments suggest that the region of the mouse genome defined by the deletions includes one or more genes regulating the expression of several structural genes that map on different chromosomes and that encode liver-cell-type specific traits.

Animals↗
PubMed1983

Plasma levels and clinical response with imipramine in a study comparing efficacy with mianserin and nomifensine.

1 The comparative antidepressant efficacy of 150 mg imipramine, 60 mg mianserin and 150 mg nomifensine was studied in 45 depressed patients in a six week double-blind investigation. 2 In the efficacy analysis of 41 patients completing the study there was no overall significant difference in efficacy between the groups. Individual group comparisons showed no significant difference in response between mianserin and nomifensine, and mianserin and imipramine. There was a significant (z = 1.99, P less than 0.05) improved response in the imipramine compared with the nomifensine treated group. The imipramine treated group were significantly older. 3 No significant plasma concentration/clinical response relationships were demonstrated with nomifensine, mianserin, imipramine or desipramine. 4 Plasma level monitoring of imipramine recommended by some investigators does not seem to be appropriate.

Adult↗
PubMed1983

Selective inhibition of thromboxane B2 accumulation and metabolism in perfused guinea-pig lung.

1 U46619, a prostaglandin H2 endoperoxide analogue and thromboxane A2 agonist, dose-dependently inhibited accumulation and metabolism of thromboxane B2 in the isolated perfused lung of the guinea-pig. At similar doses prostaglandins E1, E2, F1 alpha, F2 alpha, I2, 5, 6-trans-PGE2 and 8-iso-PGE1 were ineffective. 2 U46619 did not affect accumulation and metabolism of prostaglandin F2 alpha under similar conditions. 3 The pulmonary disposition of thromboxane B2, which occurs by uptake into pulmonary cells or binding to a specific macromolecular component, is mediated by a mechanism distinct from that handling prostaglandin F2 alpha. The possible relevance of these findings to the pulmonary disposition of thromboxane A2 is discussed.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1983

Action of 3-isobutyl-1-methylxanthine and prostaglandins D2 and E1 on histamine release from rat and guinea pig mast cells.

The action of three compounds reported to elevate intracellular cyclic adenosine monophosphate (cAMP) namely 3-isobutyl-1-methylxanthine (IBMX) and prostaglandins D2 and E1 (PGD2 and PGE1), on histamine release was examined. Three test systems were used: (i) the perfused ovalbumin-sensitized guinea pig lung and (ii) isolated cells from ovalbumin-sensitized guinea pig lung, both of which are IgG-mediated models of anaphylaxis, and (iii) an IgE model of anaphylaxis, using isolated rat peritoneal mast cells from sensitized rats. Both PGD2 and PGE1 were without effect at concentrations likely to be found during anaphylaxis. In contrast, the phosphodiesterase inhibitor, IBMX, was highly active in all three test systems. The role of raised intracellular cAMP levels in the inhibition of histamine release is discussed.

1-Methyl-3-isobutylxanthine↗
PubMed1983

Dibenamine enhancement of histamine-induced relaxation of the rabbit mesenteric artery.

Helically cut strips of rabbit mesenteric artery relax when exposed to histamine if their histamine H1 receptors are first blocked by 7 X 10(-6) M mepyramine. Relaxations are potentiated by 20 min pretreatment with 10(-6) M dibenamine. This dibenamine regimen also enhances relaxation of the strips to the selective H2 receptor agonist dimaprit, and to a lesser extent to papaverine which does not act on histamine receptors. This enhancement occurs both at 38 degrees and 22 degrees, and in mesenteric artery strips from rabbits reserpinized to deplete amine stores. Histamine has a greater relaxant effect on mesenteric artery strips at 22 degrees than at 38 degrees, normally. Dibenamine-treated strips do not relax more at the lower temperature, however. Thus, dibenamine nonselectively enhances relaxations of mesenteric artery and may enhance histamine-induced relaxations by an additional mechanism.

Animals↗
PubMed1982

Thromboxane B2 uptake and metabolism in isolated perfused lung. Identification and comparison with prostaglandin F2 alpha.

Thromboxane B2 was metabolised in isolated perfused guinea-pig lungs to a product identified by negative ion chemical ionisation mass spectrometry as 13,14-dihydro-15-ketothromboxane B2. Conversion was measured by radio TLC and was greater in guinea-pig than rat lungs (29.1 vs. 13.8% at 10 ng/ml), but similar in lungs from normal and sensitized guinea-pigs. Thromboxane B2 metabolism was less than that of prostaglandin F2 alpha but, like it, was prevented at 5 degrees C and reduced by cycloheximide pretreatment. Tissue to medium ratio in perfused guinea-pig lungs was 3.4 for thromboxane B2, but 0.2 for insulin (showing that thromboxane B2 is accumulated within the lung) and was altered after experimental manipulations. Neither lung slices, crude homogenates, cytosolic and microsomal fractions nor purified prostaglandin 15-hydroxydehydrogenase metabolised thromboxane B2 in vitro, although prostaglandin F2 alpha was extensively inactivated. Quantitative partition coefficient and albumin-binding data confirm that thromboxane B2 lacks prominent lipophilicity, implying that cellular uptake in lung must be carrier-mediated. We conclude that thromboxane B2 is a substrate for pulmonary degradation which may form a route for the biological inactivation of thromboxane A2. Its resistance to prostaglandin 15-hydroxydehydrogenase as conventionally tested remains paradoxical and is discussed.

Animals↗