Envelope representations of pinna impulse responses relating to three-dimensional localization of sound sources

Acoustical impulse responses of the external ear system are measured in order to investigate human three-dimensional auditory localization. A sound source of electric spark discharge is presented in nine directions for each of four vertical planes, 1.5 m from the center of the subject's head. The results show that a human pinna works as a compound sound reflector which produces major reflected components within 350 microseconds. The relationship between the direction of the sound source and the impulse response is clearly shown by the use of an envelope formation technique and radial ray displays.

Tumor promoters specifically and reversibly disturb development and behavior of Caenorhabditis elegans

The effect of phorbol ester tumor promoters on the development and behavior of a free-living soil nematode, Caenorhabditis elegans, was studied. When young developing C. elegans were grown on E. coli-seeded agar with low concentrations (0.1 microgram/ml) of 12-0-tetradecanoyl-phorbol-13-acetate or phorbol-12,13-didecanoate, their growth was arrested. These tumor promoters reduced the brood size when gravid adults were treated and caused uncoordinated movement in animals treated at any stage of development. The effects of these tumor promoters on nematode development and behavior were partially reversible. The nonpromoting derivatives phorbol and 4 alpha-phorbol-12,13-didecanoate showed no effect on the animals.

Specific binding of phorbol esters to Friend erythroleukemia cells--general properties, down regulation and relationship to cell differentiation

Specific and saturable binding sites for [20-3H]phorbol 12,13-dibutyrate ([3H]PDBu) were demonstrated in intact Friend erythroleukemia cells (FELC), in which inducible erythroid differentiation is reversibly inhibited by phorbol esters. The binding of [3H]PDBu to intact cells was maximal within only 15 min of incubation at 37 degrees C, after which there was a gradual decrease; binding at 4 degrees C however, was a slow process, requiring greater than 180 min for maximal binding. A Scatchard analysis showed that the dissociation constant for binding of [3H]PDBu is 8.3 nM; at saturation, approximately 1.75 x 10(5) molecules of [3H]PDBu are bound per cell. The binding of [3H]PDBu is blocked by 12-O-tetradecanoyl phorbol-13-acetate, phorbol 12,13-didecanoate, mezerein, 4-O-methyl-12-O-tetradecanoyl phorbol-13-acetate and resiniferatoxin, but not by phorbol or 4 alpha-phorbol 12,13-didecanoate. There was, in general, a good correlation between the potency of these agents in inhibiting [3H]PDBu binding and their activity in promoting tumors on mouse skin. Inducers of differentiation, such as hexamethylene bisacetamide, dimethyl sulfoxide and butyric acid, as well as inhibitors of cell differentiation, dexamethasone and local anesthetics, did not significantly block the binding of [3H]PDBu to intact FELC. When FELC were induced to differentiate with 4 mM hexamethylene bisacetamide (approximately 80% of cells were benzidine-positive), a slight decrease (10-20%) in the number of binding sites at saturation was seen, but the dissociation constant was not changed. When the cells were precultured with non-radioactive phorbol esters, a significant decrease in [3H]PDBu binding was observed, suggesting a homologous down regulation of phorbol ester receptors. Scatchard analysis indicated that the decrease in [3H]PDBu binding was due to a decrease in the number of binding sites and not to a change in affinity. Such specific phorbol ester binding sites might mediate a number of biochemical and biological effects of phorbol esters on FELC.

Tumor promoters cause a rapid and reversible inhibition of the formation and maintenance of electrical cell coupling in culture

The effect of tumor promoters on electrical coupling between human FL cells was investigated with a microelectrode technique. When a low concentration (100 ng/ml) of 12-O-tetradecanoylphorbol 13-acetate (TPA) was added to culture medium, only 6% of the cells showed electrical coupling after 5 hr, whereas in control medium more than 90% of the cells were coupled. In the presence of TPA, cell coupling remained suppressed for at least another 19 hr. When TPA was washed out from the culture medium, the cells commenced electrical coupling: 90% of the cells were coupled within 4 hr of the removal of TPA, a rate very similar to that of nontreated control cells. Therefore, TPA-mediated inhibition of cell coupling is reversible. When TPA was added to a culture in which more than 90% of the cells had already established electrical coupling, the percentage of coupled cells decreased to 6% within 8 hr, indicating that TPA can also diminish already established cell coupling. Inhibition of cell coupling also was achieved with other mouse skin tumor promoters--phorbol 12,13-didecanoate, ingenol dibenzoate, and mezerein--whereas nonpromoting derivatives--phorbol and 4 alpha-phorbol 12,13-didecanoate-showed no effect. None of these compounds changed the membrane potential, membrane resistance, or growth rate of FL cells. Thus, it appears that TPA and structurally-related tumor promoters specifically disturb the formation or function, or both, of cell-cell junctions, without significantly affecting the general properties of the surface membrane or the growth of FL cells.

Inhibition of the formation of electrical cell coupling of FL cell by tumor promoters

The effect of tumor promoters on the formation of electrical cell coupling between human FL cells was investigated by means of a microelectrode technique. In culture medium containing 100 ng/ml of 12-O-tetradecanoyl phorbol-13-acetate (TPA), only 6% of the cells were coupled after 24 hr while more than 90% of the cells were coupled in control medium. The formation of cell coupling was also inhibited by other tumor promoters, phorbol-12,13-didecanoate, ingenol-13, 20-dibenzoate and mezerein, whereas non-promoting derivatives, phorbol and 4 alpha-phorbol-12, 13 didecanoate did not affect cell coupling formation. 7, 12-Dimethylbenz [a] anthracene, benzo [a] pyrene and N-methyl-N'-nitro-N-nitrosoguanidine did not affect the cell coupling. None of the chemicals used changed any electrical properties of the cell membrane, such as membrane potential and membrane resistance, of FL cells. Thus, it appears that TPA and other related tumor promoters inhibit the formation of cell coupling without changing the physiological properties of the membrane significantly.

Inhibitory effect of tumor promoting phorbol esters and mezerein on human mixed lymphocyte reaction

The effect of phorbol ester-type tumor promoters on the mixed reaction of human lymphocytes was investigated. When a low concentration (10 ng/ml, 1.67 X 10(-8) M) of 12-O-tetradecanoylphorbol-13-acetate (TPA) was added at the beginning of the mixed lymphocyte reaction, this, as measured by [3H]thymidine incorporation, was almost completely inhibited. The inhibitory effect is apparently not related to a toxic effect, since [3H]uridine incorporation was affected to a lesser extent by the addition of TPA. TPA is also inhibitory when added after the reaction has started. The inhibition of the reaction by TPA is very rapid and complete inhibition can be seen within 2 h after TPA addition. Another promoting phorbol ester, phorbol-12,13-didecanoate )PDD), also inhibited the reaction, whereas inactive derivatives, phorbol and 4 alpha-PDD, did not. Mezerein, a weak promoter on mouse skin, was also a potent inhibitor of the human mixed lymphocyte reaction.

CT of hepatoma: effects of portal vein obstruction

CT images were studied in five patients with hepatocellular carcinoma associated with obstruction of branches of the portal vein. Two were solitary tumors located near the porta hepatis and were seen as low density areas. In addition noncancerous areas with impaired portal drainage also had lower densities than normally perfused areas. In one instance, gross and histologic studies performed on the resected specimen showed atrophy of hepatic tissue. The other three patients had disseminated tumors with multiple low density areas on CT. Additional low density areas were seen in patients with concomitant obstruction of branches of the portal vein. A decrease in portal blood flow will change the appearance of hepatocellular carcinoma of CT.

Induction of erythroleukemia cell adhesion by plant diterpene tumour promoters: a quantitative study and correlation with in vivo activities

A potent tumour promoter on mouse skin, phorbol-9-myristate-9a-acetate, induces certain clones of Friend erythroleukemia cells to become adhesive to the surface of tissue culture dishes, whereas in the absence of this compound, these cells grow in suspension. We have quantitatively tested 20 other phorbol esters and related compounds for this effect. When the results are expressed as the concentrations of compounds which show half-maximum effect on cell adhesion, the decreasing order of potency is: phorbol-9-myristate-9a-acetate (3.6 x 10(-10) M) approximately equal to gnilatimacrin greater than milliamine A approximately equal to phorbol-9,9a-didecanoate approximately equal to mezerein approximately equal to gnidilatin approximately equal to ingenol-3,20-dibenzoate greater than phorbol-9-myristate-9a-acetate greater than phorbol-9,9a-dibutyrate approximately equal to phorbol-9-9a-dibenzoate greater than 4a-O-methyl-phorbol-9-myristate-9a-acetate greater than phorbol-9-myristate-9a-acetate-3-aldehyde greater than phorbol-9,9a-diacetate greater than 2,3-dihydrophorbol-9-myristate-9a-acetate. Phorbol, 4a alpha-phorbol-9,9a-didecanoate, phorbol-3,9,9a-triacetate, phorbol-9-myristate, phorbol-9-monoacetate and phorbol-9a-monoacetate were inactive in this assay when tested at concentrations as high as 1 microgram/ml (10(-6) M). None of these 20 compounds induced adhesion when they were tested with a variant clone of Friend erythroleukemia cells which is resistant to the induction of adhesion and several other effects of phorbol-myristate-acetate. When the relative potencies of these compounds in the adhesion assay were compared to available in vivo data on tumour promoting activity on mouse skin, there was, in general, a good qualitative correlation. A better but not perfect quantitative correlation was obtained when the results from the adhesion assay were compared with reported inflammatory activity on mouse ear. When several other tumour promoters and cocarcinogens which differ structurally from the phorbol esters and related plant diterpenes were tested, none of these induced adhesion in this assay.

Computed tomography and angiography of hepatocellular carcinoma

Thirty patients with primary hepatocellular carcinoma were studied by computed tomography (CT) and angiography. Tumor images on CT could be classified into four groups according to the differences between precontrast and postcontrast scans. In comparing the findings of angiography and CT, hypervascular tumor shadows on angiography were visualized as low density areas on CT. However, in several cases, the vessel character of the tumor, hypervascularity, and prolonged capillary staining may have been responsible for the CT tumor appearance after contrast medium administration. The studies of cases with therapeutic embolization of the hepatic artery showed a marked decrease in density on CT. Patients with obstruction of branches of the portal vein had homogeneous low densities in the areas drained by the obstructed branches. Although the characteristics of the hepatic artery played an important role, portal blood flow was as significant in determining equally or more noticeably the CT appearance of hepatocellular carcinoma.

Action of phorbol esters in cell culture: mimicry of transformation, altered differentiation, and effects on cell membranes

The carcinogenic process is usually multifactor in its causation and multistep in its evolution. It is likely that entirely different molecular mechanisms underlie the many steps in this process. In contrast to initiating carcinogens, the action of the tumor-promoting phorbol esters does not appear to involve covalent binding to cellular DNA and they are not mutagenic. Recent studies in cell culture have revealed two interesting biologic effects of the phorbol esters and related macrocyclic plant diterpenes. The first is that at nanomolar concentrations they induce several changes that resemble those seen in cells transformed by chemical carcinogens or tumor viruses. These include altered morphology and increased saturation density, altered cell surface fucose-glycopeptides, decrease in the LETS protein, increased transport of deoxyglucose, and increased levels of plasminogen activator and ornithine decarboxylase. In transformed cells exposed to phorbol esters the expression of these features is further accentuated. Phorbol esters do not induce normal cells to grow in agar but they do enhance the growth in agar of certain transformed cells. The second effect of the phorbol esters is inhibition of terminal differentiation. This effect extends to a variety of programs of differentiation and is reversible when the agent is removed. With certain cell culture systems induction of differentiation, rather than inhibition, is observed. Both the transformation mimetic and the differentiation effects are exerted by plant diterpenes that have tumor-promoting activity but not by congeners that lack such activity. The primary target of phorbol esters appears to be the cell membrane. Early membrane-related effects include enhanced uptake of 2-deoxyglucose and other nutrients, altered cell adhesion, induction of arachidonic acid release and prostaglandin synthesis, inhibition of the binding of epidermal growth factor to cell surface receptors, altered lipid metabolism, and modifications in the activities of other cell surface receptors. A model of "two stage" carcinogenesis encompassing the known molecular and cellular effects of initiating carcinogens and tumor promoters is presented. According to this model, initiating carcinogens induce stable alterations in the cellular genome but these are not manifested until tumor promoters modulate programs of gene expression and induce the clonal outgrowth of the initiated cell.

Benzo(a)pyrene 7,8-dihydrodiol-9,10-oxide modification of DNA: relation to chromatin structure and reconstitution

Purified duck reticulocyte DNA was incubated in vitro with a 7,8-dihydrodiol-9,10-oxide derivative of benzo(a)pyrene (BPDE). The carcinogen-modified DNA was somewhat more susceptible to partial digestion by the single strand specific endonuclease S1 than unmodified DNA, suggesting slight denaturation of the helix at sites of modification. Chromatin was reconstituted in vitro utilizing this carcinogen-modified DNA and unmodified-chromatin associated proteins. This reconstituted chromatin showed the same kinetics and extent of digestion by Staphylococcal nuclease, and similar nucleosome profiles on sucrose density gradient centrifugation, as those obtained with native chromatin or chromatin reconstituted with unmodified DNA. Moreover, polyacrylamide gel electrophoresis of DNA fragments obtained from nuclease digests gel electrophoresis of DNA fragments obtained from nuclease digests of the reconstituted chromatins suggested that the chromatin containing carcinogen-modified DNA had the same subnucleosome structure as that reconstituted with unmodified DNA. In a separate set of studies intact duck reticulocyte chromatin was reacted directly with BPDE. Nuclease digestion studies indicated that 65% of the carcinogen was bound to the 'open' regions of chromatin, and 35% to 'closed' regions. These results indicate that although convalent binding of a benzo(a)pyrene (BP) derivative to DNA produces local distortions in conformation of the helix, this modification does not appear to interfere with the ability of the DNA to associate with histones to form nucleosome structures. In addition, although DNA in the open regions of chromatin is more susceptible to reaction with the BP derivative, there is appreciable reaction with the DNA associated with histones.

Heterogeneity of murine erythroleukemia cells with respect to tumor promoter-mediated inhibition of cell differentiation

Spontaneous and induced differentiation of murine erythroleukemia cells (strain 745A DS19 ) is reversibly inhibited by 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent promoter of mouse skin carcinogenesis, and by other tumor-promoting macrocyclic plant diterpenes, but it is not by nonpromoting diterpenes. Twelve clones randomly isolated from this strain vary in their response to TPA. All clones are induced to differentiate by several compounds, the most potent of which is hexamethylene bisacetamide. In six clones TPA (100 ng/ml) caused greater than 90% inhibition of differentiation, as measured by the appearance of benzidine-reactive cells. In two clones cell differentiation was not inhibited by TPA even at concentrations as high as 1 microgram/ml. In four clones, differentiation was only partially inhibited (16 to 47%) by TPA. Clones resistant to TPA inhibition of differentiation were also resistant to structurally related tumor-promoting agents. The isolation of variant cell lines, sensitive and resistant to TPA, provides a tool for elucidating the mechanism of tumor promoter-mediated inhibition of cell differentiation.

Tumor promoters inhibit morphological differentiation in cultured mouse neuroblastoma cells

When added to mouse neuroblastoma cultures, the potent tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) inhibits spontaneous neurite formation as well as that induced in response to serum deprivation, prostaglandin E1, 5-bromo-2'-deoxyuridine, and papaverine. Other tumor-promoting macrocyclic plant diterpenes also inhibit neurite formation, whereas nonpromoting diterpenes do not. Inhibition by TPA was reversible and was unrelated to toxicity.

Effects of n-decylamine and toluidine blue on the electric capacitance of isolated rat mast cells

The electric capacitance of isolated rat mast cells and its change under the influence of either n-decylamine or toluidine blue was investigated. Since the electric circuit employed in the detection unit is the one merely sensitive for the capacitance changes, output signals pertain to the capacitance of the tested cell alone. N-decylamine released histamine without accompanying degranulation; and it caused a marked swelling of mast cells and a striking decrease of capacitance, although electric capacitance is usually proportional to the size of the cell. Morphological changes induced by toluidine blue are seemingly correlated with the changes in capacitance. At the concentrations (25-50 microgram/ml) in which the mast cell became enlarged, electric capacitances exceeded the control value. However, at the concentrations higher than 100 microgram/ml in which the cell became shrunken, the capacitance values were less than control value. Pretreatment with DNP (0.1 mM) or oxyphenbutazone (0.05-0.2 mM) was of little effect in inhibiting the histamine release, morphological alterations and capacitance changes due to n-decylamine, but pretreatment with either prevented all of those changes produced by toluidine blue. The mechanism of the capacitance changes in mast cells induced under influence of those compounds is discussed.

Differential excision from DNA of the C-8 and N2 guanosine adducts of N-acetyl-2-aminofluorene by single strand-specific endonucleases

Purified duck reticulocyte DNA was reacted in vitro with [9-14C]-N-acetoxy-N-acetyl-2-aminofluorene. Hydrolysis of the [14C]-N-acetyl-2-aminofluorene-modified DNA followed by Sephadex LH-20 column chromatography showed that 85% of the DNA-bound [14C]-N-acetyl-2-aminofluorene was N-(deoxyguanosin-8-yl)-N-acetyl-2-aminofluorene and 15% was 3-(deoxyguanosin-N2-yl)-N-acetyl-2-aminofluorene. When this modified DNA was incubated with the single strand-specific nuclease, S1, and the undigested fraction of the DNA was analyzed, there was preferential loss of the quanosine C-8 adduct from the DNA. Moreover, analysis of the nucleosides released by exposure of N-acetyl-2-aminofluorene-modified DNA to a single strand-specific nuclease from Neurospora crassa showed only the guanosine C-8 adduct in the supernatant fraction. These results suggest that, whereas the N-(deoxyguanosin-8-yl)-N-acetyl-2-aminofluorene adduct in DNA causes major conformational changes in the double-stranded helix and localized regions of denaturation, the 3-(deoxyguanosin-N2-yl)-N-acetyl-2-aminofluorene adduct does not cause major distortions of the native DNA structure.

Tumor promoters inhibit spontaneous and induced differentiation of murine erythroleukemia cells in culture

Addition of the potent tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), to murine erythroleukemia cell lines in suspension cultures inhibited both spontaneous differentiation and differentiation induced by hexamethylene bisacetamide (HMBA), dimethyl sulfoxide, or butyric acid. Inhibition was unrelated to cytotoxicity and was reversible. When several plant diterpenes were tested, there was a positive correlation between tumor-promoting activity and inhibition of differentiation. TPA inhibited HMBA-induced differentiation only if added prior to the time of commitment to differentiation, as assayed by scoring for differentiation after transfer of cells from HMBA to fresh medium without HMBA. TPA-mediated inhibition of differentiation was associated with a decrease in globin mRNA accumulation.

Metabolism of the carcinogenic hydrocarbon benzo(a)pyrene in human fibroblast and epithelial cells. II. Differences in metabolism to water-soluble products and aryl hydrocarbon hydroxylase activity

Aryl hydrocarbon (benzo(a)pyrene) hydroxylase (AHH) activity and metabolism of benzo(a)pyrene to water-soluble products were measured in cultures of body fibroblasts and kidney epithelial cells from different human embryos. AHH activity at 24 h after treatment with or without benz(a)anthracene was determined in cultures from 23 embryos, and 3 days' accumulated metabolism of benzo(a)pyrene to water soluble products was measured in cultures from 18 embryos. The body fibroblasts from the different embryos could be divided into three groups according to the amount of water-soluble products, but not according to the AHH activity. These three groups were not found by either assay in the cultures of kidney epithelial cells. In both fibroblast and epithelial cells, high metabolism to water-soluble products was not necessarily associated with high AHH activity. The results extend our previous finding (Huberman and Sachs, 1973) of three presumably genetic groups for BP metabolism to water-soluble products in human fibroblast but not in epithelial cells and indicate that this grouping was not found in these cells by measuring AHH activity.