Biomedical subjects
D M Morgan
Publications and source records attributed to D M Morgan.
Stimulation of endothelial cell growth by sera from diabetic patients with retinopathy.
An in-vitro proliferation assay has shown that sera from patients with diabetic retinopathy, particularly those with the proliferative form, are two to four times more effective than sera from non-diabetics at stimulating 3H-thymidine incorporation into both human umbilical vein and human omental microvascular endothelial cells, but not at stimulating incorporation into human dermal fibroblasts or 3T3 cells. The factor(s) is heat stable and of molecular weight greater than 15,000, and its presence is unrelated to metabolic control. It is not present in patients with other forms of diabetic vascular disease, which suggests that it is not related to carbohydrate or lipid metabolism. These results provide evidence against the hypothesis that metabolic disturbances are central to the development of diabetic microvascular disease, and raise possibilities of novel forms of therapeutic intervention.
Effects of synthetic polycations on leucine incorporation, lactate dehydrogenase release, and morphology of human umbilical vein endothelial cells.
Naturally occurring cationic proteins secreted by human granulocytes have pro-inflammatory effects including induction of increased vascular permeability and oedema, which are likely to be mediated by damage to vascular endothelium. Synthetic cationic polyamino acids have been shown to exert similar inflammatory effects in vivo. We have therefore used a range of synthetic polycationic amino acids to investigate the characteristics required to cause endothelial cell damage, assessed by in vitro inhibition of leucine incorporation into macromolecules by human umbilical vein endothelial cells (HUVEC) in culture. Exposure of HUVEC to 20 nM-2 microM cationic polypeptides of similar Mr(av) (approximately 40,000) in the presence of 20% serum produced a dose-dependent inhibition of [3H]leucine incorporation by polymers of ornithine, arginine or lysine. Similar results were obtained using [3H]thymidine. Neutral or anionic polypeptides of similar Mr were without effect. The molar potency of polylysines increased over the range Mr 40,000-120,000, while polylysines of Mr(av) less than 25,000 had no effect. In the absence of serum, inhibition occurred more rapidly and at lower doses. Inhibition of leucine and thymidine incorporation was time-dependent, e.g. exposure to 800 nM-polylysine, Mr(av) 90,000, led to progressively increasing inhibition that was complete after 24 h exposure, and was irreversible. The effects of polycations could not be blocked by pretreatment of the cells with polyanions. Precoating of the culture surface with polylysines had no effect on leucine incorporation by HUVEC or their subsequent response to polylysines in solution. Exposure to the peptide Arg-Gly-Asp-Ser inhibited incorporation by 30% but did not increase susceptibility to polylysine.(ABSTRACT TRUNCATED AT 250 WORDS)
Oxidized polyamines and the growth of human vascular endothelial cells. Prevention of cytotoxic effects by selective acetylation.
The responses of human umbilical-vein vascular endothelial cells in culture to the naturally occurring polyamines spermine, spermidine and putrescine, their acetyl derivatives and oxidation products were examined. In the absence of human polyamine oxidase, exposure of cells to polyamines (up to 160 microM) had no adverse effects. In the presence of polyamine oxidase, spermine and spermidine were cytotoxic, but putrescine was not. Acetylation of the aminopropyl group of spermidine or both aminopropyl groups of spermine prevented this cytotoxicity. The amino acids corresponding to the polyamines, representing a further stage of oxidation, were also without effect. The cytotoxic effects were irreversible. Use of bovine serum amine oxidase in place of the human enzyme gave qualitatively similar results.
The effects of ethanol methotrexate and diphenylhydantoin on [14C] leucine incorporation by human trophoblast cells cultured in vitro.
The effects of alcohol, diphenylhydantoin and methotrexate on protein synthesis by human trophoblast have been studied in vitro using a cell culture technique. None of the drugs depressed protein synthesis at pharmacological levels and for diphenylhydantoin there was evidence that the cellular accumulation of this drug was negligible.
The effect of purified aminoaldehydes produced by polyamine oxidation on the development in vitro of Plasmodium falciparum in normal and glucose-6-phosphate-dehydrogenase-deficient erythrocytes.
Purified aminoaldehydes produced by polyamine oxidation were toxic to the malarial parasite, Plasmodium falciparum, cultured in human erythrocytes. There was a profound effect on young ring forms, and, during maturation, parasites became more sensitive to the aldehydes. Oxidation of the aldehydes abolished the lethal effect. The plasmodia within glucose-6-phosphate-dehydrogenase (G6PD)-deficient erythrocytes were more sensitive to mono- and di-aldehydes than were parasites in normal erythrocytes. G6PD-deficient erythrocytes were also more sensitive to pretreatment with the dialdehyde produced by the oxidation of spermine. Pretreatment prevented further invasion by the parasites.
Inhibition of the respiratory burst of human neutrophils by the polyamine oxidase-polyamine system.
The addition of the polyamines, spermine and spermidine, to human neutrophils caused a depression of the hexose-monophosphate (HMP) shunt activity of neutrophils stimulated with latex particles but not of unstimulated cells. The effect was dependent on the presence of bovine serum and was not observed when normal human serum was substituted for bovine serum. The polyamine oxidase (PAO) in bovine serum was probably responsible for generating the activity since normal human serum lacks PAO. A role for PAO was further supported by the finding that partially purified bovine PAO in the presence of polyamines similarly mediated inhibition of HMP shunt activity in stimulated neutrophils. Catalase failed to prevent the inhibitory effects of the PAO-polyamine system suggesting that H2O2 is not the responsible product. In addition, our results show that human pregnancy serum known to contain PAO activity in the presence of polyamines mediated a similar inhibition of the respiratory burst.
Differences in sensitivity of Schistosoma mansoni schistosomula, Dirofilaria immitis microfilariae, and Nematospiroides dubius third-stage larvae to damage by the polyamine oxidase-polyamine system.
The effect of the polyamine oxidase (PAO)-polyamine system on some helminths was examined in vitro. Both Schistosoma mansoni schistosomula and Dirofilaria immitis microfilariae were highly sensitive to this system, the latter more so than the former. In contrast, exsheathed third-stage larvae of Nematospiroides dubius were resistant to the effects of the PAO-polyamine system. After incubation of microfilariae with either spermine or spermidine in the presence of serum containing PAO (bovine serum or human retroplacental serum) or partially purified PAO, damage of worms occurred, compatible with our criteria for worm death. Similar results were obtained with schistosomula by using spermine. The damage seemed to be mediated by PAO products other than hydrogen peroxide because catalase did not protect either parasite. Our data demonstrate that helminths may be damaged by products of the PAO-polyamine system.
Photoelectroanalytical chemistry: electrochemical detection of a photochemically active species, tris(2,2'-bipyridine)ruthenium(II).
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Long-term culture of human trophoblast cells.
A technique is presented for the preparation of cultures of replicating human trophoblast cells from term placentas. The adherent cells obtained were very slow growing (doubling time 12.5 days) as measured by the rate of increase in cell protein, [14C]-leucine uptake and cell number. Cells from individual placentas have been maintained in continuous culture for up to 1 year (10-12 passages) and have been successfully recultured after storage in liquid nitrogen. Cultured cells showed positive immunofluorescent staining for human placental lactogen, human chorionic gonadotrophin, transferrin and type IV collagen. The adenine nucleotide content indicated that energetically the cells were in balance even after prolonged culture.
Theoretical and practical limitations on the optimization of amperometric detectors.
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Noise and signal-to-noise ratio in electrochemical detectors.
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Mid-trimester pregnancy--a time of tranquility or activity?
A number of compounds in pregnancy blood reach a maximum or minimum concentration at around 20-24 weeks of pregnancy, a period of conspicuous clinical tranquility. The compounds mostly derive from either fetal tissue or decidua and it is suggested that they may be part of an elaborate mechanism which controls invasion of the uterine wall by trophoblast.
Serum polyamine oxidase activity in normal pregnancy.
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Photoelectroanalytical chemistry: possible interferences in serum and the selective detection of tris(2,2'-bipyridine)ruthenium(II) in the presence of interferents.
Photoelectroanalytical chemistry, the application of photoelectrochemistry to analysis, as reported here, is based on the amperometric detection of tris(2,2'-bipyridine)ruthenium(III) after its production from the corresponding Ru(II) complex in an excited state and quenching by electron transfer. The Ru(II) complex is detectable in concentrations less than 10(-10) mol/L injected into a flow stream in 100 microL. The selectivity of the detection is based upon several competitive reactions and their rates. The complex can be detected accurately in the presence of at least 10(4) molar excess of the potent interferents uric acid and oxalic acid. We anticipate that this complex will be used in assays that involve the use of labels.