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Single-layer organic light-emitting diodes (OLEDs) are highly desired due to their potential advantages such as simplifying the fabrication process and lowering the cost. However, high-performance single-layer OLEDs are rare in the literature as they require bipolar transporting materials with balanced electron and hole mobilities, high fluorescent quantum yields, and good energy levels matching both electrodes. In this work, a bipolar transporting benzanthracene derivative, namely 7,12-bis-[4-(2,2-diphenylvinyl)-phenyl] benzanthracene (BDPBan), is designed and synthesized without any structural motifs for hole and electron transport. As electrons and holes can perform intermolecular hopping to similar spatial extents between the adjacent benzanthracene moieties, well-balanced hole and electron mobilities higher than 10−3 cm2/Vs are achieved. Though the strong intermolecular interactions facilitate the formation of excimers in concentrated solutions and thin films of BDPBan, efficient undoped single-layer OLEDs are fabricated with strong green emission from the excimers. A device with 90 nm BDPBan as the emitting layer shows a peak current efficiency of 11.4 cd/A: beyond the conventional upper limit calculated based on the photoluminescence quantum yield.

The basicity constants of eleven methyl 1,2-benzanthracenes and the absorption spectra of their conjugate acids were measured in anhydrous hydrofluoric acid. It could be shown that in every case two isomeric ions, in which the proton has reacted with either of the two meso carbon atoms, were present. The basicity constants of the conjugate acids could be determined. The relative increase of this constant on methyl substitution is compared with theory.

I) A new synthesis of 4′‐methyl‐1,2‐benzanthracene (XII) starting from 1‐naphthaldehyde, is described. This synthesis involves the following steps: bromination (5‐bromo‐1‐naphthaldehyde), Wolff‐Kischner reduction (5‐bromo‐1‐methylnaphthalene), Grignard condensation with phthalic anhydride (5′‐methyl‐α‐naphthoyl‐o‐benzoic acid), cyclisation (4′‐methyl‐1,2‐benzanthraquinone), reduction (4′‐methyl‐1,2‐benzanthracene). II) 4′9,10‐trimethyl‐1,2‐benzanthracene (III) has been prepared: a) By a Grignard reaction between methyl‐magnesium iodide and 4′‐methyl‐1,2‐benzanthraquinone (see above) by the method of Sandin and Fieser. b) starting from 1,2‐benzanthraquinone by the following steps: bromination (4′‐bromo‐1,2‐benzanthraquinone), Grignard condensation with methyl‐magnesium iodide (4′‐bromo‐9,10‐dimethyl‐1,2‐benzanthracene) treatment with C4 H9 Li and (CH3)2 SO4 (4′, 9, 10‐trimethyl‐1,2‐benzanthracene). Copyright © 1952 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim

A detailed QSPR investigation of the water solubility (logS) of 1063 solid neutral chemicals, agrochemicals, drugs and prodrugs has been carried out. The application of the "General Solubility Equation" of Yalkowsky et al. resulted in a correlation between experimental and calculated solubility with rather modest statistic criteria. It was found that 191 compounds (18%) have calculated logS with deviations above one logarithmic unit. A comparison of experimental values with those calculated by an equation previously derived for liquid chemicals demonstrates that a part of the total set of compounds containing certain substructures such as chloroalkyls, phenyls, biphenyls, nitrogen (acyclic and in cycles), benzanthracenes, phenols, and chemicals with ether, ester, and N,N-disubstituted carboxamide groups obey to the equation for liquids. Not unexpectedly, the other part of compounds containing both strong H-bond acceptor and donor groups is essentially less soluble than calculated for compounds in the liquid state. It is proposed that this low solubility is connected with a specific H-bond association of these compounds in their crystal lattice. Two approaches were tested for the derivation of quantitative models for prediction of the solubility of solid chemicals and drugs. The first approach is based on the QSPR for liquids extended by several indicator variables for different functional groups. The second approach is based on the combination of chemical similarity and traditional QSAR techniques. In the framework of this approach different numbers of structural and physicochemical neighbors of a compound-of-interest were considered together with the corresponding HYBOT descriptor data. This method enables to calculate the solubility of a compound-of-interest by using the solubility of nearest neighbor compounds and the difference between descriptor data of those neighbors and the corresponding data of the compound-of-interest. It was found that the use of nearest neighbor compounds with high Tanimoto index value (i.e. good structural similarity) and close H-bond acceptor and donor factors (good physicochemical similarity) ensures good prediction of water solubility with average absolute errors on the level of the error of experimental logS determination.

The thermal reaction of hexacarbonylchromium with the polycyclic aromatic hydrocarbons (PAHs) pyrene, perylene, chrysene and 1,2-benzanthracene has afforded four organometallic complexes of the type [(η6-PAH)Cr(CO)3], whose unprecedented structures were obtained by single-crystal X-ray analysis. The topology of the coordination of the Cr(CO)3 fragment and its asymmetry with respect to the coordinating ring may depend on the opportunity to maintain the maximum aromaticity of the complexed ligand. DFT calculations, 1H NMR, FT-IR and Raman spectroscopy have been used to elucidate the type of interaction between the PAH ligand and the carbonylmetal moiety, giving insight into the ligand-to-metal donor capacity and the intra- and intermolecular interactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The results of quantitative structure-activity relationship (QSAR) studies on six series of compounds exhibiting indirect mutagenic activity are reported. These findings demonstrate the importance of frontier orbital energies and, in some cases, frontier orbital electronic populations to overall mutagenicity in diverse polyaromatic hydrocarbons, benzidines and aminobiphenyls, benzonitrofurans, nitrogenous cooked-food mutagens, benzanthracenes, and chrysenes. The correlations between structural parameters and mutagenic potency vary from R=0.81 to R=0.97, and these findings are discussed in the context of possible molecular mechanisms of mutagenicity. In particular, it is generally regarded that cytochrome P450-mediated activation of polyaromatic hydrocarbons and their amino derivatives plays an important role in mutagenic activity. In this respect, it is apparent that enzymes of the cytochrome P4501 (CYP1) family are closely associated with the metabolic activation of polyaromatic mutagens and carcinogens via the generation of reactive intermediates (usually electrophilic in nature) that attack DNA. The findings presented in this study indicate that QSAR analyses on several series of compounds are consistent with the known evidence of procarcinogen activation mechanisms, particularly for polyaromatic hydrocarbons and their heterocyclic/amino derivatives, pointing to the importance of frontier orbital energy values in particular. Teratogenesis Carcinog. Mutagen. Suppl. 1:187–193, 2003. © 2003 Wiley-Liss, Inc.

The action of benzo(a)pyrene (BP), 3-methylcholanthrene (3MC), benzanthracene (BA), and 7,12-dimethylbenzanthracene (DMBA), four polycyclic aromatic hydrocarbons (PAHs), was studied on the unicellular protozoan Tetrahymena pyriformis. This ciliatewas exposed to the PAHs at 1, 15, and 37 μM for up to 6 h. BP and BA caused a slight inhibition of cell growth, whereas 3MC and DMBA showed no detectable effect. Cell viability remained unaffected by the PAHs at all concentrations and exposure times tested. Cellular accumulation of PAHs was studied using flow cytometry. The results show immediate accumulation followed by rapid elimination of the compounds. BP uptake was also studied in the presence of verapamil and cyclosporin, compounds known as inhibitors of the multidrug resistance (MDR) pump. In the presence of verapamil, BP was accumulated in larger amounts in cells. With cyclosporin, the accumulation of the PAH was several times higher than under control conditions. The results of GC/MS analysis show that PAH elimination was not linked to biotransformation. These results suggest that the resistance of Tetrahymena against PAH cytotoxicity may be attributed to the rapid efflux of these agents from the cells via an efflux pump probably of the MDR type. Cytometry 28:170–175, 1997. © 1997 Wiley-Liss, Inc.

Polycyclic aromatic hydrocarbons (PAH) are a common component of soil pollution, yet little is known of the ecotoxicological risks these compounds may pose to life in soil. This article reports the ecotoxicity of five PAHs for two terrestrial isopod species. Isopods were exposed to food contaminated with four different concentrations of either fluorene, phenanthrene, fluoranthene (up to 4 μmol/g), benz[a]anthracene, or benzo[a]pyrene (up to 1.25 μmol/g). Exposure of Porcellio scaber lasted 16 weeks, and no adverse effects on survival, growth, or total protein (only females tested) were observed in any of the treatments. A small but significant reduction in growth of Oniscus asellus was observed at 47 weeks of exposure to 0.125 μmol benz[a]anthraceneṁg−1 dry weight and 1.25 μmol fluoreneṁg−1 dry weight and higher concentrations. A significant stimulation of the reproduction of O. asellus was observed in some of the phenanthrene, fluoranthene, benz[a]anthracene, and benzo[a]pyrene treatments; a larger proportion of the females were gravid, which resulted in a higher number of juveniles per female. Exposure did not significantly affect brood size, weight of the mother after release of the juveniles, or the survival of the juveniles upon starvation. Total protein content of females was significantly reduced at 0.4 μmol fluorene g−1 dry weight and higher concentrations. Growth and protein content of isopods is likely to be affected by PAH exposure only at highly contaminated sites. The ecological consequences of stimulated reproduction and possible DNA damage are poorly understood and require further attention because soil invertebrates may be exposed to PAHs over many generations.

The functionalized benzanthracenes are useful synthons which can be converted into derivatives such as (V) and (VIII) as well as polycyclic carbazoles like (X).

Immune function and hepatic MFO activity were examined in adult and nestling starlings administered a synthetic PAH, 7,12-dimethylbenz[a]anthracene (DMBA). Methods used to examine the starling immune system included immunopa-thology, macrophage phagocytosis, lymphocyte blastogenesis to concanavalin A, and hemagglutination of sheep erythrocytes (SRBC). Concomitant investigations of MFO activity were conducted in starlings exposed to DMBA. Ethoxyresorufin O-dealkylase (EROD) and pentoxyresorufin O-depentylase (PROD) were used as indicators of hepatic MFO activity. Changes in MFO activity were compared to chemically altered immune responses following DMBA exposure. Subcutaneous exposure of adult starlings to 125 mg/kg DMBA resulted in suppression of lymphocyte blastogenesis and antibody production to SRBC. EROD and PROD activity were increased 2.8- and 3.4-fold, respectively. Lymphocyte blastogenesis was impaired in adult starlings orally exposed to 125 mg/kg DMBA. The immune system of nestling starlings exposed orally to 100 mg/kg DMBA was altered, as evidenced by decreased phagocytic ability of macrophages and inhibition of lymphocyte blastogenesis. Oral exposure to DMBA did not induce MFO activity in starlings of either age class. Effects of DMBA on immune function and MFO activity in starlings varied with the age of birds and route and length of chemical exposure.

A quantitative structure-activity relationship (QSAR) has been derived for the mutagenic activity of 117 aromatic and heteroaromatic nitro compounds acting on Salmonella typhimurium TA100. Relative mutagenic activity is bilin-early dependent on hydrophobicity, with an optimal log P of 5.44, and is linearly dependent on the energy of the lowest unoccupied molecular orbital of the nitro compound. The dependence of mutagenic activity on hydrophobicity and electronic effects is very similar for TA98 and TA100. Mutagenic activity in TA100 does not depend on the size of the aromatic ring system, as its does in TA9. The effect of the choice of assay organism, TA98 versus TA100, on nitroarene QSAR is seen to be similar to the effect previously found for aminoarenes. Lateral verification of QSARs is presented as a tool for establishing the significance of a new QSAR.

Experiments were performed to study the early and late ultrastructural changes during hamster cheek pouch carcinogenesis using a regimen of topical application of 9,10 dimethyl-1-1-2 benzanthracene (DMBA) twice a week in liquid paraffin oil. The DMBA was administered for a period of 2 and 4 1/2 months. Hamsters exposed to DMBA for 2 months developed moderate precancerous changes, whereas the hamsters treated with DMBA for 4 1/2 months developed frank and multiple oral tumors with a cauliflower appearance. The ultrastructural pathological changes seen were considerably increased at 4 1/2 months compared with a 2 month period of DMBA treatment. Untreated and solvent control hamsters cheek pouch treated for 2 and 4 1/2 months with liquid paraffin oil alone did not show any premalignant or malignant changes during this period.

An ab initio STO-5G computational analysis of the electrostatic potentials of four structural analogs of the highly toxic 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and four related aromatic systems (benzo(a)pyrene, benz(a)anthracene and two isomeric benzoflavones) was carried out. The systems, to varying degrees, induce aryl hydrocarbon hydroxylase activity and are believed to interact with the same cytosolic receptor in initiating their biochemical responses. It was found that a high degree of activity appears to require negative potentials that are non-overlapping above all or most of the lateral regions, with an observed optimum range of magnitudes. In systems with central oxygens, it is required that the negative oxygen potentials be small and weak; however, oxygen negative regions in the molecule are not necessary for high activity. The observed differences between the potential patterns of the four aromatic systems and those of TCDD and its active analogs may reflect an inherent dissimilarity in the nature of their interactions with the cytosolic receptor.

We have demonstrated the utility of an Escherichia coli microsuspension assay to detect and characterize chemical mediation of DNA damage by a wide variety of mutagens and carcinogens. The assay have been improved by the development of a microsuspension modification to the Bacillus subtilis ''rec'' assay. The addition of these gram-positive organisms has allowed detection of DNA damage induced by benzo(a)pyrene (B(a)P), 3-aminopyrene (3-AP), 7, 12-dimethylbenz(a)anthrancene (DMBA), 3-methylcholanthrene (3-MC), and 4-nitrobiphenyl (4-NBP). Data presented in this paper from tests of 61 additional compounds, including a representative number of direct and promutagenic agents, indicate that the B subtilis H17 and M45 strains provide an effective microbial system for identification of DNA damage susceptible to postreplicational repair. The results of this study further suggests that the inclusion of these strains in the microsuspension assay for DNA damage will markedly enhance the detection of agents which cannot readily penetrate the intact cell wall of E coli.

A component capable of binding benzo(a)pyrene was measured in plasma from cigarette smokers and nonsmokers. This plasma fraction was found to have a high specificity of binding to benzo(a)pyrene, bound benzanthracene competitively with benzo(a)pyrene, and was positively correlated (r = 0.861, p less than 0.001) with the capacity of the individual subject's lymphocytes to be induced for AHH activity in culture. An inverse correlation (r = -0.957, p less than 0.001) between the presence of the plasma component in lung cancer patients and the capacity of lung cancer patients' lymphocytes to be induced in culture is unexplained at this time. A benzo(a)pyrene-binding fraction was not found in induced or uninduced cultured lymphocytes from smokers or nonsmokers, or in homogenates of lung excisional tissue from smokers with or without primary lung cancer.

Fur Benzoldiazonium-tetrafluoroborat und eine Anzahl p-substituierter Derivate werden ermittelt: Geschwindigkeitskonstanten der photochemischen Elektronenubertragung von Pyren bzw. Benzanthracen auf das Diazoniumsalz in Acetonitril (Bestimmung durch Loschung der Fluoreszenz des Elektronendonors); Geschwindigkeitskonstanten der Elektronenanlagerung unter den Bedingungen der Pulsradiolyse in tert-Butanol/Wasser; Quantenausbeuten und Produktzusammensetzung (ArOMe, ArF bzw. ArH) bei der Photolyse in Methanol in Gegenwart verschiedener Konzentrationen an 2-Methyl-2-nitrosopropan zur Inhibierung der nachfolgenden thermischen Kettenreaktion. Die Elektronenubertragung bzw. -Anlagerung ist diffusionskontrolliert, kE = 2 …; 3 × 1010 l/mol · s. Fur den Gesamtverlauf wird ein kinetisches Modell aufgestellt, mit dessen Hilfe aus den Mesdaten absolute Geschwindigkeitskonstanten fur folgende Teilreaktionen erhaltlich sind: H-Ubertragung innerhalb des Kafig-Radikalpaares (Bildung von ArH), kH ≈ 1011 s−1; Maximalwerte fur die Photosolvolyse (Bildung von Ar⊕ ArOMe bzw. ArF), ks ≲ 1011 s−1; Abfang der Arylradikale auserhalb des Losungsmittelkafigs durch t-BuNO, kq ≈ 2 × 107 l/mol· s. Die Ergebnisse werden im Zusammenhang mit dem aufgestellten kinetischen Modell und weiteren Befunden diskutiert. Kinetics and Mechanism of Aryldiazonium Salt Photolysis in Methanol. Determination of Absolute Rate Constants of Some Reaction Steps For benzene diazonium tetrafluoroborate and some p-substituted derivatives, the following values are determined: velocity constants for the photochemical electron transfer from pyrene and benzanthracene to aryl diazonium salts in acetonitrile solution (determination by quenching the donor fluorescence). velocity constants for electron transfer under the condition of pulse radiolysis in tert.-butanol-water solution; quantum yields and product composition (ArOMe, ArF and ArH, respectively) for the photolyses in methanol in the presence of varying concentrations of 2-methyl-2-nitroso-propane as a quencher of the thermal chain reaction. The electron transfer reaction comes out be a diffusion controlled reaction, kE = 2 … 3 × 1010 M−1 s−1. For the total reaction a kinetic model is set up which affords absolute velocity constants from the experimental results for the following steps: Hydrogen transfer within the case radical pair (formation of ArH) kH ≈ 1011 s−1; Maximal values for the photo-solvolyses (formation of Ar⊕ ArOMe and ArF, respectively), ks ≲ 10−1; Trapping of aryl radicals outside of the solvent cage by t-BuNO, kq ≈ 2 × 107 M−1 s−1. The results are discussed in the light of the kinetic model and some other facts.

Polymers were prepared from 4,4′-diphenoxydiphenylsulfone, isophthaloyl dichloride, and bis-p-phenoxyphenyl-4,4′-(2,2′-dibromodiphenyl)ketone, 2,2′-dibromodiphenyl-4,4′-dicarbonyl dichloride, or bis-p-phenoxyphenyl-4,4′-(2,2′-diphenylethynyldiphenyl)ketone in Friedel-Crafts type of polymerization. Bromine groups were subsequently replaced with phenylacetylene residues, and the polymers were cured at high temperatures, with the apparent formation of benzanthracene linkages. Cured polymers exhibited higher softening points, decreased solubilities, and, in some instances, higher melting points than their uncured precursors. Significant weight losses occurred during isothermal aging tests.

Hepatoma cells derived from the Reuber H35 rat hepatoma express cytochrome P450 enzymes of two major families: polycyclic aromatic hydrocarbon-inducible forms are found in both differentiated and dedifferentiated cells while phenobarbital (PB)-inducible forms are found only in differentiated cells. We report here that (i) benzanthracene and PB induce P450 c mRNA in differentiated and dedifferentiated cells and (ii) dexamethasone and PB induce P450 b/e and/or P450 PB1 mRNAs in differentiated cells but not in dedifferentiated cells.

Several steroid responsive stromal cell strains were isolated from normal mouse endometrium. Both estrogen responsive and progesterone responsive strains were obtained. The estrogen responsive cells were also responsive to diethylstilbestrol (DES). The progesterone responsive strains were inhibited by estrone and estriol. One of the estrogen responsive cell strains, E041, was cloned in the presence and absence of 17-beta-estradiol (E2). Of 14 clones developed in the absence of E2 and screened for responsivity of growth, six were significantly responsive to E2. Six of 26 clones developed in the presence of E2 were responsive to E2. Microsomes isolated from these clones were shown to have aryl hydrocarbon hydroxylase (AHH) activity which was inducible with either benzanthracene (BA) or 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD). The basal levels of AHH activity were significantly reduced by E2 in E2 responsive clones. The TCDD induced levels of AHH activity in the E2 responsive and E2 non-responsive clones were significantly reduced by E2. The BA induced levels of AHH were significantly increased by E2 in one of the clones. These results show that mouse endometrial stroma consists of a number of populations of cells with different specific proliferative and metabolic responses to steroids.

Chylomicrons obtained from the thoracic duct of rats fed [3H]7,12-dimethylbenz(a)anthracene (DMBA), a polycyclic aromatic hydrocarbon, were infused intravenously into rats with bile fistulas. Over 17 hr, 55.9 +/- 3.2% (mean +/- SEM) of the radioactivity was recovered in bile and 6.7 +/- 0.5% in urine. Minor amounts were deposited in liver, kidneys and epididymal fat pads. Injection of DMBA in ethanolic solution gave a similar pattern, while biliary DMBA metabolites resulted in higher recovery in urine and lower recovery in fat. In conclusion, the major part of chylomicron DMBA is rapidly excreted via the biliary route, while a fraction is probably retained in adipose tissue.

C3H/StWi mice spontaneously lost their exogenous MMTV (MMTV-S) in 1958 and became a low mammary cancer subline. They do not ordinarily express their endogenous MMTV provirus as virions. Virigin C3H/StWi females were exposed to chemical carcinogens, 7-12 dimethyl(α)benzanthracene (2,6 mg) and urethane (200 mg) in the presence or absence of chronic hormonal stimulation of the mammary gland by pituitary isografts. By 10 months of age, mammary tumors developed in 40% of the females given DMBA, and in 59% of those given DMBA and carrying pituitary isografts. With urethane treatment alone, 14% of the mice developed mammary cancer during a 12-months period; however, 74% of the mice bore mammary tumors when pituitary isografts were present. None of the females given pituitary isografts alone developed mammary cancer during the experimental period. Mammary tumors from each group were evaluated by radioimmune competition assay, immunoperoxidase and electron microscopy to determine the extent of endogenous MMTV gene expression. In addition, the mammary glands of some of the non-tumor-bearing mice were studied by whole mount and by histology to determine the type, extent, and number of mammary dysplasias present in each group. In general, there was no correlation between tumor incidence and the presence of mammary tumor virus antigens. Of 32 mammary tumors tested in all groups, 10 were positive at low levels for MMTV antigens. In the positive tumors, the internal MMTV gag gene antigen, p28, was prevalent. Immunoperoxidase studies on these same tumors gave quantitatively similar results. It is apparent from these observations that chemical carcinogenesis of mouse mammary glands does not require or even favor the complete expression of endogenous MMTV genes. In this study, hormonal stimulation of the glands during and after exposure to the carcinogen increases the rate of tumorigenesis, but does not seem to favor MMTV gene expression. We conclude that C3H/StWi mice are susceptible to DMBA and urethane induction of mammary cancer and to an extent this process is positively influenced by the presence of hormonal stimulation. Our results support the view that a qualitative or quantitative shift in the expression of MMTV proviral sequences does not occur during tumor development.

The 13C13C spin coupling constants have been determined in substituted [1-13C]tetrahydronaphthylenes, [5-13C]hexahydrobenzanthracenes and [5-13C]benzanthracene. In addition, the 13C13C spin coupling constants for 7-hydroxy[7-13C]benzopyrene, trans-7,8-dihydro[7-13C]benzopyrene-7,8-diol and trans-7,8-dihydro[10-13C]benzopyrene-7,8-diol are reported, together with the one-bond carbon-carbon coupling constants between C-4 and C-5 in selected 4,5-disubstituted benzopyrenes. Values for the directly bonded coupling constants and long-range coupling constants are similar to those reported previously for other aromatic and aliphatic systems. Substituent effects on carbon-carbon coupling are compared for similarly substituted cyclic and acyclic systems.

The response of the hair follicle apparatus to topical 9, 10-dimethyl-benzanthracene applications was studied in several strains of mice and rats. Early follicular destruction in mice was associated with subsequent formation of large number of epithelial tumors. Preserved follicular structures in rats proliferated with the formation of low incidence of adenomas and trichoepitheliomas. Hair nevi, hairfollicle nevi and trichofolliculomas, unrelated to treatment, were observed in several animal strains.

Six-week-old female BDF1 mice were treated with a single topical application of DMBA followed by repeated application of TPA on the clipped dorsal skin. Several weeks after DMBA application, the intradermal melanocytes of perifollicular melanocytic network began to proliferate to form melanocytic tumors in all treated mice skin. Besides these changes, single membrane-bound melanosomes and premelanosomes were found in the cytoplasm of perineural epithelia and Schwann cells with mesaxons of the nerve bundles involved, and the melanogenic activity of the Schwann cell and the perineural epithelium of the dermal peripheral nerve bundle was discussed in terms of a common feature of neuro-ectodermal cells.

It has been reported in earlier papers that aromatic additives can reduce the rate of radiation-induced degradation of poly(methyl methacrylate) (PMMA), depending on the concentration, the distribution, and the resonance of the aromatic system. In the present work, the temperature dependence is studied, together with the influence of molecular mobility, which is determined by the physical state of the system. For this purpose, PMMA containing benzene, biphenyl, naphthalene, anthracene, phenanthrene, pyrene, or benz[a]anthracene, was γ-irradiated at room temperature and also, except with naphthalene and biphenyl, in the temperature range −80 to 160°C. The changes in degradation rate were related to the first excited singlet state and to the resonance energy of the additives. The results suggest that at low temperatures both electron scavenging and transfer of excitation energy occur. At temperatures between the γ transition and the glass transition, the significance of energy transfer compared with electron scavenging increases, whereas the inhibitory effect decreases. Above the glass transition temperature the inhibition decreases more rapidly. This is related to scavenging of radical chain fragments, due to increasing molecular mobility, which causes a decrease in recombination rate. This sensitization of degradation competes with the inhibition by energy transfer and electron scavening, and may prevail at temperatures above 185°C. The opposing effects of these mechanisms can be clearly shown with the system PMMA–benzene. In viscous mixtures, sensitization prevails even at room temperature.

In order to increase the sensitivity of the C3H/10T1/2 CL8 (10T1/2) cell transformation system, the chemical exposure period was increased to a total of 6 days (two consecutive 3-day exposures). Using this modified procedure, we transformed 10T1/2 cells with procarcinogens such as aflatoxin B/sub 1/, benz(a)anthracene, and 4-nitroquinoline-1-oxide which have been negative in the standard 10T1/2 cell transformation assay. However, ..beta..-naphthylamine was inconclusive and 2-acetylaminofluorine was negative in this modified assay system. Results demonstrate that a simple modification of the 10T1/2 cell transformation method can increase the sensitivity to some procarcinogens that require metabolic activation.

Delayed fluorescence (DF.) spectra of 1,2-benzanthracene, fluoranthene, pyrene, and chrysene in methylcyclohexane were measured at −80° up to the wavenumber corresponding to the energy of two triplets. With all four compounds a weak DF. Sn S0 from the highest state Sn accessible by triplet-triplet annihilation (TTA) was found. Lifetimes of Sn calculated (a) from the ratio of the DF's Sn S0 and S1 S0 and (b) from the difference in line-width of the 0,0-transitions Sn,0 S0,0 and S1,0 S0,0 agree reasonably well. This indicates that population of the highest accessible excited singlet state is the dominating primary process in the excited singlet channel of TTA. There is no evidence for excimer formation being the first step in TTA. DF. spectra extend up to the energy of two triplets. With pyrene the intensity distribution in the hot-band region of the DF. S2 S0 suggests that in TTA the same vibrational selection rules are valid as in one-photon absorption S2 S0 and that vibrational relaxation within the S2 manifold is slow compared with internal conversion S2 ↝ S1. The experimental technique is described in detail and experimental difficulties arising from impurities and photoproduct formation are discussed.

1 Aryl hydrocarbon hydroxylase (AHH), a mixed-function oxidase system, has been identified in microsomal preparations of adult breast skin and foreskin. 2 Separation of dermis from epidermis by stretching, showed that AHH activity in human skin is almost exclusively located within the epidermis. 3 Preincubation of whole chopped skin with benzanthracene (5 muM to 100 muM) using a tissue culture system was accompanied by a concentration dependent increase in AHH activity. 4 Although there was no significant difference in AHH activity between the two sites, individuals differed markedly from one another in activity at any one site. Activity was observed to be positively correlated with age.

Liver homogenates or extracts of liver homogenates from rats in which portacaval shunt had been performed were found to have a significant growth-promoting effect on 7,12 dimethyl (a) benzanthracene (DMBA)-produced breast carcinoma in rats. Tumor potentiation was manifested by increased incidence of animals developing tumors, increased number of tumors, and increased tumor size, when compared with animals receiving injections of shunted or control liver. These observations suggest the existence of a tumor-stimulating factor in liver from which portal blood has been completely and chronically diverted by portacaval shunt. The demonstration of tumor growth stimulating factor(s) present in shunted liver, together with previously reported observations of the modification of the growth of various types of tumors in animals with a portacaval shunt, suggests that the liver is capable of playing an important role in tumor-host interactions. The portacaval shunt appears to be useful as a technique in elucidating ways that liver function may influence tumor growth.

The structures of proton-addition complexes of aromatic hydrocarbons were hitherto known only with respect to their stoichiometric compositions but can now be clarified by ultraviolet, infrared, and NMR spectroscopic methods. For example, it has been possible to prove by NMR soectroscopy that the expected addition of protons into 9,10-dimethyl-[a] benzanthracene actually does take place. Two isomeric proton adducts of toluene have been found by means of infrared spectra. On addition of protons, the ultraviolet spectra of aromatics change considerably; excellent agreement is sometimes observed between the band maxima calculated by quantum mechanics and those found by experiment.

Hamster cheek pouches were painted three times weekly for 2 to 12 weeks with 0.5% 9-10 dimethyl 1-2 benzanthracene (DMBA) and/or 10% vitamin A dissolved in liquid paraffin. With vitamin A alone, foci of acanthosis first appeared after 4 weeks. After DMBA alone for 6 weeks intraepithelial carcinoma was present. However, after only 4 weeks application of the combination of DMBA and vitamin A, intraepithelial carcinomas were found and after 6 weeks infiltrating carcinomas were present. After 8 weeks infiltrating carcinomas were also present in pouches treated with DMBA alone but at this stage, as well as after 10 and 12 weeks, the combination of DMBA and vitamin A had induced more anaplastic and larger tumors than DMBA alone. These findings may be the result of an addition of the epithelial hyperplasia effected by vitamin A and the carcinogenic effect of DMBA. Alternatively, the increased permeability of cellular and subcellular membranes induced by vitamin A may facilitate the entry of DMBA into the cells, thus potentiating its carcinogenic effect.

SUMMARY 1 4-Ethylsulphonylnaphthalene-1-sulphonamide has been shown to be carcinogenic to the epithelium of the bladder of the mouse. The female mouse is more susceptible than the male. 2 The prior administration of a potent carcinogen, 9: 10-dimethyl-1: 2-benzanthracene, did not significantly affect the yield of tumours induced by the chemical. 3 The hyperplastic activity of the agent has been shown to be apparent as early as two days after the start of treatment and to be induced by 0–0025 per cent, of the chemical in the diet of the C57 X IF mouse. There is a considerable variation in the sensitivity of different strains of mouse to its action. 4 A number of chemicals of a structure similar to the hyperplastic agent have been tested for hyperplastic activity to the bladder epithelium. Some slight modifications of the structure did not abolish the activity but most of the analogues tested were inactive.

SUMMARY Rats with one kidney removed showed a progressive increase in weight of the remaining kidney over a six-week period. Autoradiographic and radiochemical studies with 3H-thymidine indicated that the increase in new kidney cell formation was maximal forty-eight to seventy-two hours after unilateral nephrectomy. This early response was chiefly due to the production of new cells by the renal cortical tubules. Normal rates of tubule cell turnover were achieved two weeks after operation. The glomerular tufts contained fewer new cells and their peak production was delayed to the one-week period with a slow decline thereafter. Rats forty-eight hours after unilateral nephrectomy were chosen as a model to study the effect of various substances on the magnitude of new cell formation. The number of DN A-synthesising cells in the stimulated kidney was reduced by treatment with hydrocortisone, ACTH, 9,10-dimethyl-1,2-benzanthracene, and 1,2-benzanthracene; the numbers were increased by the administration of deoxycorticosterone and aldosterone.

Delayed fluorescence (DF.) spectra of 1,2-benzanthracene, fluoranthene, pyrene, and chrysene in methylcyclohexane were measured at −80° up to the wavenumber corresponding to the energy of two triplets. With all four compounds a weak DF. Sn S0 from the highest state Sn accessible by triplet-triplet annihilation (TTA) was found. Lifetimes of Sn calculated (a) from the ratio of the DF's Sn S0 and S1 S0 and (b) from the difference in line-width of the 0,0-transitions Sn,0 S0,0 and S1,0 S0,0 agree reasonably well. This indicates that population of the highest accessible excited singlet state is the dominating primary process in the excited singlet channel of TTA. There is no evidence for excimer formation being the first step in TTA. DF. spectra extend up to the energy of two triplets. With pyrene the intensity distribution in the hot-band region of the DF. S2 S0 suggests that in TTA the same vibrational selection rules are valid as in one-photon absorption S2 S0 and that vibrational relaxation within the S2 manifold is slow compared with internal conversion S2 ↝ S1. The experimental technique is described in detail and experimental difficulties arising from impurities and photoproduct formation are discussed.