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R D Estensen

Publications and source records attributed to R D Estensen.

At least 37 records · Page 2Linked to original sources
PubMed1985

Urokinase-type plasminogen activator in alveolar macrophages and bronchoalveolar lavage fluid from normal and smoke-exposed hamsters and humans.

Our purpose was to identify and characterize plasminogen activator (PA) activity in alveolar macrophages (AMs) and lower respiratory tract fluid from hamsters and humans. Freshly harvested hamster AMs had barely detectable PA intracellularly and no detectable activity in concentrated lavage fluid. PA secretion was detected in conditioned media of hamster AMs. Secretion was enhanced sixfold by phorbol myristate acetate (PMA) and suppressed by dexamethasone. In contrast to hamsters, PA activity was readily detected in lysates of freshly harvested human AMs and lavage fluid. However, secretion of PA by human AMs was not detected, and neither PMA nor dexamethasone affected PA activity. PA from hamster or human AMs has a urokinase-type enzyme with molecular weights of 49,000 or 55,000, respectively. Cigarette smoking did not alter PA activity by hamster or human AMs.

Adult↗
PubMed1984

Concanavalin A and alloxan interactions on glucose-induced insulin secretion and biosynthesis from islets of Langerhans.

The pretreatment of isolated islets of Langerhans with concanavalin A (Con A) completely blocks alloxan from suppressing the insulin release response to glucose. The lectin itself inhibits insulin secretion. This effect is dose dependent and reversible. Con A, however, has no protective action against the inhibition of glucose-induced insulin biosynthesis in islets exposed to alloxan. The protective action of Con A on alloxan toxicity is likely to be at the beta-cell surface at a membrane recognition site for glucose as a stimulus for secretion. The insulin biosynthetic effect of glucose appears to be mediated through a separate mechanism.

Alloxan↗
PubMed1984

Phorbol myristate acetate: is a tumor promoter acting as a hormone?

Tumor promoters act on carcinogen-initiated tissues to cause phenotypic expression of malignancy. Phorbol ester tumor promoters, like hormones, act on cells and tissues at nanomolar concentrations, often producing "physiological" effects. These promoters also act on cells to produce what appear to be nonphysiologic or toxic effects. One of the major questions regarding these phenomena is, Which action or actions of promoters are important in phenotypic expression of malignancy?

Animals↗
PubMed1984

Analysis of human promyelocytic leukemia cell (HL60) variants insensitive to phorbol ester tumor promoters.

The cells of the human promyelocytic leukemia cell line (HL60) stop growing and differentiate into macrophage-like cells when exposed to nM concentrations of the phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). By exposing cells to the frameshift mutagen ICR-191 and subsequently selecting for resistance to the differentiating effects of nM amounts of TPA, we have isolated TPA-insensitive variants. These variants can grow in up to 320 nM TPA concentrations and do not differentiate into morphologically or functionally mature macrophages. The number of phorbol ester receptors, their affinity for phorbol dibutyrate, and the regulation of receptors are the same as for wild-type HL60 cells. As the resistance to TPA increases in the variants, so does the number of cells with increased ploidy. Wild-type HL60 cells are nearly 100% hypodiploid with a modal chromosome number of 43, while a partially TPA-resistant variant (DM30) has 30% hyperdiploid cells with a mean chromosomal number of 70, and a completely resistant variant (DM90) is 93% hyperdiploid averaging 74 chromosomes/cell. The variants differentiate into neutrophils in response to dimethyl sulfoxide but are defective in respiratory burst activity as assayed by the reduction of the dye nitroblue tetrazolium. These variants could be useful in determining the mode of action of TPA in the promotion of tumors.

Caenorhabditis elegans Proteins↗
PubMed1983

Action of 12-O-tetradecanoylphorbol-13-acetate on Y1 adrenal cells apparently requires the regulatory subunit of type 1 cyclic AMP dependent protein kinase.

Y1 mouse adrenal tumor cells and mutants of Y1 cells (Kin 2 and Kin 8), with defects in regulatory subunit of type 1 protein kinase (R1), were assayed for steroid, growth, and plasminogen activator after application of the tumor promoter 12-O-Tetradecanoylphorbol-13-acetate (TPA). TPA, like ACTH, caused an increase in steroid production and a decrease in growth in Y1 cells. The effects on steroidogenesis were diminished in Kin 2 and markedly diminished in Kin 8. TPA induced plasminogen activator in Y1 but not Kin 2 or Kin 8 while ACTH induced the enzyme in both Y1 and Kin 2 but not Kin 8. TPA did not produce a measurable increase in cyclic nucleotides in Y1 cells. Unlike Cytochalasin E, another agent that causes steroidogenesis without changes in cyclic AMP concentration, TPA and ACTH did not require serum for its effect on steroid production. Cytochalasin E also caused induction of plasminogen activation in Y1, but not in Kin 2 or Kin 8 cells. TPA however produced growth inhibition in both mutant cell types while ACTH produced a progressively diminishing growth inhibitory effect in Kin 2 and Kin 8. The results suggest that a portion of TPA action on Y1 cells requires R1.

Adrenal Cortex Hormones↗
PubMed1980

Lack of correlation between effects of tumor promoter TPA on plasminogen activator production, phosphatidyl choline synthesis, and hexose transport in mammalian cell culture systems.

We have investigated the effects of the tumor promoter 12-0-tetradecanoyl-phorbol-13-acetate (TPA) on plasminogen activator production, hexose transport and metabolism, and the incorporation of choline into the acid soluble pool and into phosphatidylcholine in suspension cultures of mouse L, mouse P388 leukemia, human HeLa, and Chinese hamster ovary cells, and in monolayer cultures of baby hamster kidney (BHK), mouse 3T3, mouse 3T6, and mouse P388D1 macrophage-like cells. BHK, 3T3, P388D1, and P388 cells produced plasminogen activator constitutively, but no significant production was observed in the other cell lines. Plasminogen activator production was induced or stimulated by TPA only in P388 cells (10- to 20-fold by 100 ng TPA/ml). On the other hand, phosphatidylcholine synthesis was stimulated by TPA only in HeLa cells, and hexose transport, as measured with 3-0-methyl-D-glucose, only in 3T3 and P388D1 cells, as well as in human lymphocytes. The stimulation of hexose transport occurred more rapidly than the induction of plasminogen activator production and seemed to be part of the mitogenic response of cells to TPA treatment. A stimulation of deoxyglucose uptake was similarly limited to 3T3 and P388D1 cells. A significant decarboxylation of carbon 1 of deoxyglucose occurred in P388 and P388D1 cells, but not in Novikoff cells, and any decarboxylation that occurred was not stimulated by TPA. The results indicate that the various investigated responses of cells to TPA are unrelated and occur independent of each other. The time courses of the biochemical responses also differ significantly.

Animals↗
PubMed1980

Plasminogen activator of islets of Langerhans: modulation by glucose and correlation with insulin production.

Islets of Langerhans isolated from rat pancreas contain and secrete plasminogen activator (PA). Production of PA is increased up to 15-fold by culture in the presence of high concentrations of glucose, and the dose-response curves for the effect of glucose on secretion of PA and on insulin are superimposable. Alloxan, a diabetogenic agent that is selectively cytotoxic for beta cells, abolishes the PA response to glucose. Various agents and hormones that affect beta-cell function affect the secretion of PA in a manner parallel to their modulation of insulin secretion. These observations suggest that PA is produced by beta cells and that enzyme synthesis and secretion are regulated in concert with those of the hormone. The potential role of PA and of plasmin in the physiology of the islets is considered. In particular, because plasmin cleaves proinsulin to a product that is electrophoretically indistinguishable from insulin, it is suggested that the PA/plasmin system may play a part in the conversion of proinsulin to the active hormone.

Alloxan↗
PubMed1980

Binding of [3H]12-O-tetradecanoylphorbol-13-acetate to intact human peripheral blood lymphocytes.

Our studies indicate that tritiated 12-O-tetradecanoylphorbol-13-acetate ([3H]TPA) produced by the reduction of the C-20 aldehyde with sodium [3H]borohydride is recognized by the same cellular site as is unlabeled 12-O-tetradecanoylphorbol-13-acetate (TPA). None of the concentrations of TPA used in these studies had an effect on the cell number and viability of human peripheral blood lymphocytes (HPBL) when incubated up to 1 hr at temperatures of 37 and 4 degrees as compared to untreated controls. [3H]TPA was not significantly metabolized by these cells after 1 hr at 37 degrees. Examination of the binding of [3H]TPA with simultaneous examination of uptake of tritiated thymidine ([3H]dThd) in parallel cultures demonstrated a close correlation between the apparent binding constant (0.94 X 10(8) M-1) and the activation constant for TPA stimulation of [3H]-dThd incorporation (0.95 X 10(-8) M). Binding of [3H]TPA was examined in two experimental conditions in which TPA-induced mitogenesis was inhibited: (a) preincubation of HPBL at 37 degrees for 24 hr causes a decrease of [3H]dThd uptake of 50% and an apparent loss of binding sites for [3H]TPA; and (b) glucocorticoid inhibition of [3H]dThd uptake in HPBL by 50%, however, did not reduce [3H]TPA binding. Our data suggest that cellular receptors either at the membrane or in the cytoplasm exist for TPA in HPBL. Alterations in binding of TPA to these receptors may account for the decrease in mitogenic response in preincubation experiments.

Adult↗
PubMed1978

Phorbol myristate acetate: effect of a tumor promoter on insulin release from isolated rat islets of Langerhans.

Phorbol myristate acetate (PMA), a tumor-promoter capable of influencing biologic functions of many cell systems, has been demonstrated to augment glucose-initiated insulin release from isolated rat islets of Langerhans. PMA caused a 2-fold increase in insulin release. This effect of PMA did not alter the sigmoidal relationship of insulin released to glucose concentration. The effect of PMA on insulin secretion from the islet beta-cells persists and a challenge with glucose alone, subsequent to a pulse of PMA, elicits an augmented insulin release response.

Animals↗
PubMed1976

Role of Ca2+ and Mg2+ in some human neutrophil functions as indicated by ionophore A23187.

Studies with the divalent cation ionophore A23187 suggest that both Ca2+ and Mg2+ ion influx play a role in human peripheral blood neutrophil function. Degranulation of neutrophils occurred at ionophore concentrations of 10(-5) M and was Ca2+ but not Mg2+ dependent. Modulation of neutrophil chemotaxis was enhanced optimally by 10(-7) M ionophore and was both Ca2+ and Mg2+ dependent. Concentrations of ionophore as low as 10(-12) M seemed to sensitize the cells to a concentration of phorbol myristate acetate which by itself was not chemotactic. These findings also indicate that factors other than Ca2+ or increases in cyclic nucleotides are important to initiation and modulation of neutrophil function.

Anti-Bacterial Agents↗
PubMed1976

Severe staphylococcal disease associated with allergic manifestations, hyperimmunoglobulinemia E, and defective neutrophil chemotaxis.

Neutrophil granulocyte function was determined in three patients with systemic staphylococcal infection, clinical manifestations of generalized allergic disease, and hyperimmunoglobulinemia E. Each of the patients had urticarial skin rashes before or at the time of development of staphylococcal suppurative lymphadenitis, pneumonia, or sepsis. Neutrophil chemotaxis, random migration, phagocytosis, and bactericidal capacity were assessed to determine if an abnormality in these functions might have contributed to the development of severe staphylococcal infections. Each of the three patients with generalized urticaria was found to have a marked defect in neutrophil chemotaxis. The mean chemotactic index of the patients was 12 +/- 4, whereas that of 20 controls was 72 +/- 11. Neutrophil random migration, phagocytosis, and bactericidal capacity were normal in each patient. The serum or plasma of the patients did not inhibit chemotaxis of control neutrophils and did not contain an increased concentration of the chemotactic-factor inactivator found in normal serum. Treatment of the neutrophils of these three patients with the competitive histamine H2 receptor blocking agent, burimamide, produced a significant increase in chemotactic responsiveness. These studies suggest the possibility of pharmacologic modification of neutrophil granulocyte function.

Burimamide↗
PubMed1975

Membrane effects of cytochalasin B. Competitive inhibition of facilitated diffusion processes in rat hepatoma cells and other cell lines and effect on formation of functional transport sites.

Cytochalasin B competitively inhibits the transport of 2-deoxy-D-glucose and thymidine in a number of different cell lines (Novikoff rat hepatoma cells, mouse L, S180 and Ki-MSV-transformed BALB/3T3 cells, and human HeLa cells). The apparent Km values for the transport of these substrates as well as the apparent Ki values for the inhibition by cytochalasin B are very similar for the various cell lines, and the effect is readily and completely reversed by removal of the chemical. Thymidine transport by Chinese hamster ovary cells however, is little affected by cytochalasin B, whereas the transport of 2-deoxy-D-glucose, uridine and guanine by these cells is competitively inhibited to about the same extent as in other cell lines. In addition and concomitant with the inhibition of cytokinesis and an alteration in cell shape, cytochalasin B also impairs and delays the formation of functional transport sites for thymidine, guanine and choline in synchronized populations of Novikoff cells without affecting the apparent affinities of the transport systems for their substrates. This effect is unrelated to the direct inhibition of the transport processes, since the drug does not directly inhibit choline transport and has no effect on the formation of 2-deoxy-D-glucose transport sites in spite of the fact that it strongly inhibits the transport of this substrate. The inhibition of functional transport sites may be due to the induction of a structural alteration in the membrane by cytochalasin B which impairs the insertion of new proteins of certain but not all transport systems into the membrane.

Binding Sites↗
PubMed1975

Modulation of human neutrophil chemotactic responses by cyclic 3',5'-guanosine monophosphate and cyclic 3',5'-adenosine monophosphate.

Cyclic 3',5'-guanosine monophosphate (cGMP) and cyclic 3',5'-adenosine monophosphate (cAMP) and compounds known to effect the intracellular concentrations of these nucleotides were examined for their ability to effect human neutrophil (PMN) responsiveness to chemotactic stimulation. Incubation of neutrophils with agents recognized to promote increases in intracellular cAMP in a variety of tissues (i.e., epinephrine, norepinephrine, isoproterenol, histamine, cholera toxin, and prostaglandin E-1 and E-2) or with cAMP inhibited the leukotactic response to a bacterial chemotactic factor. In contrast, cGMP and compounds which have been shown to promote increases in intracellular cGMP concentration (i.e., acetylcholine, carbamylcholine, phorbol myristate acetate, and prostaglindin F-2-alpha) markedly enhanced the neutrophil chemotactic response. The inhibitory or stimulatory influences on chemotactic responsiveness promoted by several of the agents could be shown to be blocked by a specific pharmacologic antagonist of the particular compound tested. These data support the hypothesis that cGMP and cAMP can provide opposing regulatory influences on certain cellular functions; in this case, directed motility of leukocytes.

Acetylcholine↗
PubMed1974

Selective labilization of specific granules in polymorphonuclear leukocytes by phorbol myristate acetate.

The action of phorbol myristate acetate (PMA), the active principle of croton oil, on polymorphonuclear leukocytes (PMNs) has been evaluated in this study. Small amounts of PMA caused the rapid development of vacuoles in neutrophils and the disappearance of specific granules. Histochemical and cytochemical studies revealed that alkaline phosphatase activity was transferred to vacuoles and disappeared from the cells, while myeloperoxidase activity remained associated with intact azurophilic lysosomes. Electron-dense tracers indicated that the vacuole membranes originated, at least in part, from the cell wall of the neutrophils. The results indicate that PMA stimulates events remarkably similar to those which take place when bacteria are engulfed by PMNs, except for the failure of azurophilic lysosomes to participate in PMA-induced vacuole formation. PMA appears to be the first chemical agent capable of inducing selective labilization of specific granules in the neutrophil.

Alcohols↗
PubMed1974

Investigation of the release reaction in platelets exposed to phorbol myristate acetate.

Phorbol myristate acetate (PMA), the active principle of croton oil, is a potent platelet aggregating agent. Previous cytochemical and electron microscopic studies demonstrated that PMA caused selective labilization of platelet storage granules resulting in their conversion to distended vacuoles. Communication was established between the enlarged, almost empty vacuoles and the surrounding plasma through channels of the open canalicular system. The present study has explored the possibility that the effect of PMA on platelet storage organelles stimulates a process of secretion. Analysis of the release reaction in platelets after exposure to PMA revealed that significant amounts of serotonin and adenine nucleotides were secreted without loss of lactic dehydrogenase. Release took place well before the onset of irreversible aggregation. Inhibitors of platelet secretion or ADP induced aggregation could modify or prevent the irreversible clumping stimulated by small concentrations of PMA. Although the secretion induced by PMA differed from the release caused by other agents, the findings of the present study indicate that PMA is capable of triggering the platelet release reaction.

Adenine Nucleotides↗
PubMed1974

Ultrastructural features on the platelet response to phorbol myristate acetate.

Phorbol myristate acetate (PMA) the active ingredient of croton oil, is a potent stimulus of irreversible platelet aggregation. The present study has examined the effects of PMA on platelet fine structure during aggregation and after incubation. PMA appears to act primarily on channels of the open canalicular system and intracellular granules. Small amounts of the agent cause dilatation of some open channels and conversion of granules to swollen vacuoles. Platelet discoid shape is not affected significantly by the changes in channels and vacuoles, and aggregation occurs without shape change. EDTA inhibits PMA-induced aggregation but does not prevent the conversion of platelet granules to vacuoles. In unstirred systems PMA causes similar changes in platelet fine structure and spontaneous aggregation. The drug appears to affect the permeability barrier separating granule contents from open channels, thereby leading to osmotic swelling of the storage organelles. PMA is the first agent observed to have a selective influence on the stability of platelet granules.

Alcohols↗