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Biomedical subjects

D O Adams

Publications and source records attributed to D O Adams.

At least 109 records · Page 6Linked to original sources
PubMed1982

Chilling-Induced Ethylene Production in Cucumbers (Cucumis sativus L.).

1-Aminocyclopropane-1-carboxylic acid (ACC) level, ACC synthase activity, and ethylene production in cucumbers (Cucumis sativus L.) remain low while the fruit are held at a temperature which causes chilling injury (2.5 degrees C) and increase rapidly only upon transfer to warmer temperatures. The increase in ACC synthase activity during the warming period is inhibited by cycloheximide but not cordycepin or alpha-amanitin. Our data indicate that the synthesis of ACC synthase, which results in increased ACC levels and accelerated ethylene production, occurs only upon warming, possibly from a message produced or unmasked during the chilling period. Ethylene production by chilled (2.5 degrees C) cucumbers increased very little upon transfer to 25 degrees C if the fruit were chilled for more than 4 days. The fruit held for 4 days or longer showed a large increase in ACC levels but little ethylene production even in the presence of exogenous ACC. This suggests that the system which converts ACC to ethylene is damaged by prolonged exposure to the chilling temperature. Cucumbers stored at a low but nonchilling temperature (13 degrees C) showed very little change in ACC level, ethylene production, or ACC synthase activity even after transfer to 25 degrees C.

Journal Article↗
PubMed1982

Recycling of 5'-methylthioadenosine-ribose carbon atoms into methionine in tomato tissue in relation to ethylene production.

The ribose moiety of 5'-methylthioadenosine (MTA) is metabolized to form the four-carbon unit (2-aminobutyrate) of methionine in tomato tissue (Lycopersicon esculentum Mill., cv. Pik Red). When [U-(14)C-adenosine] MTA was administered to tomato tissue slices, label was recovered in 5-methylthioribose (MTR), methionine, 1-aminocyclopropane-1-carboxylic acid (ACC), C(2)H(4) and other unidentified compounds. However, when [U-(14)C-ribose]MTR was administered, radioactivities were recovered in methionine, ACC and C(2)H(4), but not MTA. This suggests that C(2)H(4) formed in tomato pericarp tissue may be derived from the ribose portion of MTA via MTR, methionine and ACC. The conversion of MTR to methionine is not inhibited by aminoethoxyvinylglycine (AVG), but is O(2) dependent. These data present a new salvage pathway for methionine biosynthesis which may be important in relation to polyamine and ethylene biosynthesis in tomato tissue.

Journal Article↗
PubMed1982

Mechanisms of target recognition and destruction in macrophage-mediated tumor cytotoxicity.

Macrophages can be activated to kill neoplastic cells selectively and efficiently. Recent studies from his laboratory on mechanisms of target recognition and injury operative in such lysis have centered on the binding of tumor targets to the secretion of a cytolytic protease (cytolytic factor (CF]) by activated murine macrophages. Activated macrophages selectively and extensively bind neoplastic cells; nonselective binding of a low degree is seen between numerous cell pairs. The selective binding of three nonadherent tumors, which is much firmer than the nonselective binding, appears to depend on shared recognition structures contained within plasma membranes of the three tumors. Activated macrophages also secrete a potent, cytolytic, serine protease of molecular weight approximately 40,000. Secretion of CF is closely correlated with activation for cytolysis, and specific protease inhibitors of CF block macrophage-mediated cytotoxicity. Binding of tumor cells to activated macrophages triggers augmented secretion of CF. Several lines of evidence indicate that the capacity for selective binding and the capacity for secreting CF are separate and independently regulated functions of activated macrophages and that each is necessary but not sufficient for completion of macrophage-mediated tumor cytotoxicity. Analysis of the complete lytic interaction between activated macrophages and tumor cells suggests that binding and then secretion of CF are sequentially involved. These data have been integrated into a minimal hypothetical model, which suggests that macrophage-mediated tumor cytotoxicity is a multistep event encompassing 1) selective binding of tumor cells to the surface of activated macrophages and 2) secretion of multiple lytic effector substances, including CF, from the activated macrophages.

Animals↗
PubMed1982

The capacity of activated murine macrophages for augmented binding of neoplastic cells: analysis of induction by lymphokine containing MAF and kinetics of the reaction.

The capacity for augmented binding of tumor cells is an initial and necessary part of macrophage-mediated tumor cytotoxicity. To study the induction of binding capacity, we obtained FCS-elicited, inflammatory macrophages from C57BL/6J mice. Exposure of these macrophages to lymphokine(s) containing MAF induced augmented binding capacity in a dose-dependent fashion. Resident peritoneal macrophages did not respond to lymphokine, and endotoxin did not appreciably influence induction of binding. Maximum induction of binding required continuous interaction between macrophages and lymphokine for 6 to 10 hr. The conditions necessary for induction of binding closely paralleled those for induction of priming or cytolysis. Exposure of FCS-elicited macrophages from C3H/HeJ mice, although not of macrophages from A/J mice, induced augmented binding. The data suggest that the augmented capacity for binding tumor cells is induced by lymphokine(s) and that a major part of induction of priming for cytolysis by MAF is induction of such binding.

Animals↗
PubMed1982

The relationship between competence for secretion of H2O2 and completion of tumor cytotoxicity by BCG-elicited murine macrophages.

BCG-elicited macrophages from C3H/HeJ and A/J mice secrete H2O2 comparably to BCG-elicited macrophages from control C3H/FeJ mice in response to the pharmacologic stimulant phorbol myristate acetate. By contrast, BCG-elicited macrophages from C3H/HeJ and A/J mice could not effect tumor cytotoxicity, whereas macrophages from the control C3H/FeJ mice could. When BCG-activated macrophages from C57BL/6J mice were held in culture overnight, their ability to secrete H2O2 in response to the pharmacologic trigger declined 40 to 60%; the presence of endotoxin in the overnight cultures did not alter competence for secretion of H2O2. By contrast, the cultured macrophages lost all of their cytolytic competence, but this competence could be fully maintained by the presence of endotoxin in the cultures. In three distinct circumstances, competence for secretion of H2O23 thus did not correlate with competence for completion of tumor cytotoxicity. The data imply that competence for release of H2O2 is not sufficient for completion of tumor cytotoxicity.

Animals↗
PubMed1981

Binding of bacillus Calmette-Guérin-activated macrophages to tumor targets. Selective inhibition by membrane preparations from homologous and heterologous neoplastic cells.

The binding of tumor cells by activated macrophages is an initial and necessary event in the cytolysis of these targets. The data here indicate that membrane preparations from RL sigma 1 leukemia targets, EL-4 lymphoma targets, and P815 mastocytoma targets each inhibited binding of its homologous target to bacillus Calmette-Guérin (BCG)-activated murine macrophages in a dose-dependent fashion. Similar amounts of membrane from lymphocytes did not alter binding of the three neoplastic target to BCG-macrophages. Membranes of the three targets also inhibited binding of the heterologous neoplastic targets. Inhibitory activity of membrane preparations from P815, EL-4, and RL sigma 1 targets could be adsorbed by incubation of limiting concentrations of the membrane preparations with BCG-activated macrophages but not with thioglycollate broth-elicited macrophages. Exposure of BCG macrophages to membrane preparations from RL sigma 1, FL-4, or P815 targets inhibited subsequent cytolysis of the three targets. Inhibitory activity was increased in preparations enriched for plasma membrane. The data suggest that binding of three murine, nonadherent neoplastic targets to BCG-activated murine macrophages is mediated, in part, by recognition structures present within the plasma membranes of the three targets.

Adsorption↗
PubMed1981

Simple and sensitive assay employing stable reagents for quantification of plasminogen activator.

A simple and sensitive indirect assay for quantifying plasminogen activator using [3H]-casein as substrate is described. The assay has been used to measure plasminogen activators from various sources including bacteria, cultured cells, and human plasma. The assay is linear with respect to concentration of plasminogen activator and time of incubation and is independent of concentration of plasminogen. The assay can routinely be used to quantify as few as 8 X 10(-3) international units ml-1 of streptokinase. Results obtained with the [3H]-casein assay correlate well with those obtained by the fibrin plate method (R = 0.83 by Spearman's ranked co-efficient of correlation). The reagents are extremely stable and easily stored. The ease with which the assay can be performed gives the clinical laboratory the potential to test large numbers of patients upon short notice and within a short period of time.

Animals↗
PubMed1981

Characterization of genetic defects in macrophage tumoricidal capacity: identification of murine strains with abnormalities in secretion of cytolytic factors and ability to bind neoplastic targets.

Peritoneal macrophages from BCG-infected C3H/HeJ or A/J mice, in contrast to BCG-activated macrophages from C3H/HeN mice, were ineffective at lysing adherent 1023 sarcoma targets, nonadherent P815 mastocytoma targets, or nonadherent EL-4 lymphoma targets. The ability of macrophages from BCG-infected C3H/HeJ mice to secret cytolytic factor (CF) into the supernatant medium was markedly impaired. This secretory deficit, however, did not extend to plasminogen activator, secretion of which was augmented. In contrast, the ability of BCG macrophages from A/J mice to secrete CF was comparable to or even slightly higher than that of macrophages from C3H/HeN mice. The ability of BCG-elicited macrophages from A/J mice to bind either of 2 neoplastic targets (the P815 mastocytoma and the EL-4 lymphoma), however, was greatly reduced. The ability of BCG-elicited macrophages from C3H/HeJ mice to bind these targets was comparable to that of macrophages from C3H/HeN mice. The data suggest that the phenotypically-similar deficits in tumoricidal capacity of BCG-elicited macrophages from C3H/HeJ and A/J mice are mediated by mechanistically different defects in macrophage-tumor cell interactions.

Animals↗
PubMed1981

The binding of BCG-activated macrophages to tumor targets stimulates secretion of cytolytic factor.

The binding of neoplastic targets and the secretion of a potent cytolytic protease (CF) by BCG-activated macrophages have previously been shown to be independent functions, both of which are necessary for completion of macrophage-mediated cytolysis. The present studies demonstrate that secretion of CF is triggered by the binding of neoplastic targets to BCG-activated macrophages. The binding of tumor targets, but not of normal lymphocytes, resulted in enhanced secretion of CF from BCG-activated macrophages, although not from macrophages elicited by thioglycolate broth. Dead or metabolically inactive tumor targets, as well as membrane preparations of tumor targets, induced secretion of CF from BCG-activated macrophages. The blocking of macrophage-target binding with a porous filter prevented augmented secretion of CF. Appreciable secretion of CF occurred in as little as 30 min after addition of tumor targets to BCG macrophages. Binding did not induce a generalized increase in secretion of neutral proteases by BCG macrophages, since secretion of plasminogen activator was actually decreased after the binding of P815 targets. The data suggest the selective binding of BCG-activated murine macrophages to neoplastic targets triggers the secretion of a potent CF.

Animals↗
PubMed1981

The ADCC capacity of macrophages from C3H/HeJ and A/J mice can be augmented by BCG.

Macrophages elicited from the peritoneal cavity of C3H/HejJ and A/J mice by bacillus Calmette-Guérin (BCG), although ineffective in mediating tumor cytotoxicity, had augmented capacity to mediate antibody-dependent cellular cytotoxicity (ADCC) against both erythroid and neoplastic target cells. The level of augmented ADCC was comparable to that expressed by BCG-activated macrophages from control C3H/HeN mice. The data suggest that the defective potential for cytolytic activation in 2 genetically deficient strains of inbred mice does not extend to augmentation of capacity for mediating ADCC and that full expression of cytolytic activation is not necessary for expression of augmented cytolysis of antibody-coated targets.

Animals↗
PubMed1981

The role of transmethylation reactions in regulating the binding of BCG-activated murine macrophages to neoplastic target cells.

The ability of BCG-activated macrophages from C57BL/6J mice to lyse neoplastic targets was depressed by inhibitors of methyltransferase reactions (10(-4) M adenosine, 10(-5) M EHNA, and 10(-4) M L-homocysteine or 10(-5) M DZA). Binding of P815 mastocytoma targets to BCG-activated macrophages, which has been shown to be a necessary event in cytolysis of those targets, was also inhibited by adenosine, EHNA, and L-homocysteine or by DZA at the above concentrations. Inhibition of binding was obtained when macrophages were pretreated with the inhibitors, whereas pretreatment of targets with the inhibitors did not alter binding. The inhibitors were not toxic to the macrophages, as judged by morphology and viability of the macrophage cultures as well as by ability of macrophages to bind antibody-coated P815 targets or to secrete plasminogen activator. The inhibitors, at concentrations that inhibited cytolysis and binding, also depressed one type of S-adenosyl-L-methionine-mediated methylation reaction (protein carboxy-O-methylation) in BCG macrophages. The data suggest that transmethylation reactions are essential for the ability of BCG activated murine macrophages to bind and, hence, to destroy P815 tumor cells.

Animals↗
PubMed1981

Hydrogen peroxide and cytolytic factor can interact synergistically in effecting cytolysis of neoplastic targets.

Two secretory products from activated macrophages, which are thought to be involved in the lysis of tumor cells, are H2O2 and cytolytic factor (CF). To examine the potential of interaction between these 2 mediators of cytolysis, we first exposed MCA-I sarcoma targets to the 2 lytic agents. MCA-I targets, which have been previously shown to be lysed by CF, could also be lysed by H2O2 (the concentration of H2O2 causing 50% lysis of targets was approximately 1.4 x 10(-3) M). Exposure of the MCA-I targets to a nonlytic concentration of H2O2 for 1 hr potentiated the subsequent lytic effects of CF and did so synergistically. Exposure of targets to CF, however, did not potentiate the subsequent lytic effects of H2O2, even when the targets were treated with a lytic concentration of CF for 4 hr. Similar results were seen with P-388 lymphoma targets. The P388 cells were quite sensitive to the lytic effects of H2O2 (the concentration of H2O2 causing 50% lysis of these targets was approximately 2.0 x 10(-5) M) but proved relatively resistant to CF in comparison to the MCA-I targets. The data suggest that H2O2 and CF can interact synergistically to produce cytolysis of neoplastic targets if the targets are exposed to the 2 substances in a defined sequence.

Animals↗
PubMed1980

Inhibition of ethylene production by 2,4-dinitrophenol and high temperature.

2,4-Dinitrophenol (DNP) and high temperature (35 to 40 C) are known to inhibit C(2)H(4) production in various plant tissues. The present study was made to determine the step in the C(2)H(4) biosynthetic pathway (methionine --> S-adenosylmethionine [SAM] --> 1-aminocyclopropane-1-carboxylic acid [ACC] --> C(2)H(4)) at which these treatments exert their inhibitory effect. In mung bean hypocotyls the dose-inhibition curves for the effect of DNP on auxin-dependent C(2)H(4) production (in which auxin exerts its effect by stimulating the conversion of SAM to ACC) and on ACC-dependent C(2)H(4) production (in which ACC is directly utilized as precursor) were similar. It was concluded, therefore, that DNP at low concentrations (below 50 micromolar) exerted its effect primarily on the conversion of ACC to C(2)H(4), a step which is common to both systems. This view was further substantiated by quantitative analysis of the intermediates in the biosynthetic sequence. DNP exerted little influence on the content of SAM but caused a significant increase in the ACC content and marked inhibition in C(2)H(4) production, indicating that the conversion of ACC to C(2)H(4) is the crossover point. At higher concentrations (above 100 micromolar), DNP inhibited the conversion of methionine to ACC and to C(2)H(4), and this effect could be attributed to the inhibition of SAM synthesis.The optimal temperature for maximal C(2)H(4) production by apple tissue and mung bean hypocotyl is about 30 C. An increase in temperature to 35 C caused an accumulation of endogenous ACC, whereas C(2)H(4) production was greatly reduced. These results suggest that the conversion of ACC to C(2)H(4) is highly vulnerable to high temperature inhibition.

Journal Article↗
PubMed1980

Ethylene Production by Chilled Cucumbers (Cucumis sativus L.).

Chilling at 2.5 C accelerated the synthesis of 1-aminocyclopropane-1-carboxylic acid (ACC) and C(2)H(4) production in cucumber fruit. Skin tissue contained higher levels of ACC and was more sensitive to chilling than was cortex tissue. Accumulation of ACC in chilled tissue was detected after 1 day of chilling and remained elevated even after C(2)H(4) production started to decline. These data suggest that ACC synthesis is readily stimulated by chilling, whereas the system that converts ACC to C(2)H(4) is vulnerable to chilling injury. Chilling-induced C(2)H(4) production was inhibited by amino-ethoxyvinylglycine, sodium benzoate, propyl gallate, 2,4-dinitrophenol, carbonyl cyanide m-chlorophenylhydrazone, and cycloheximide. The utilization of methionine for ACC formation and chilling-induced C(2)H(4) biosynthesis was established using l-[3,4-(14)C]methionine. Chilled tissue had a higher capacity to convert l-[3,4-(14)C]methionine to ACC and C(2)H(4) than did nonchilled tissue.

Journal Article↗