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Resume Dans le but de diminuer les effets phototoxiques et la genotoxicite de la PUVA therapie, le pyrido (3,4-C) psoralene (PP) et le 7-methylpyrido (3,4-C) psoralene (MPP) ont ete synthetises et etudies. Leur absorption maximale dans les UVA se situe respectivement a 325 et 330 nm. Leur photostabilite est comparable a celle du 8-MOP. Ils se complexent au DNA dans le noir et, en presence d'UVA, ils ne produisent que des monoadditions sur le DNA comme le prouvent les etudes de fluorescence et de denaturation-renaturation du DNA. Dans les levures eucaryotes diploides, ils sont plus efficaces que le 8-MOP dans l'induction d'effets lethaux et de dommages mitochondriaux. Leur activite mutagene par unite de dose d'UVA est du meme ordre que celle du 8-MOP. Cependant, ils sont clairement moins mutagenes que le 8-MOP en fonction de la survie. Cette difference est aussi observee pour l'activite recombinogene. Ils n'ont pas d'effet oxygene. Dans les cellules de mammiferes, la comparaison des effets biologiques donne les resultats suivants: inhibition de la synthese du DNA dans les fibroblastes humains: MPP > PP > 8-MOP; activite mutagene dans les cellules V79 de hamster chinois MPP > PP > 8-MOP; capacite de transformation de cellules embryonnaires de souris C3H: MPP > 8-MOP > PP en fonction de la dose d'UVA, 8-MOP > MPP > PP en fonction de la survie. Induction d'echange de chromatides sœurs (SCE) par unite de dose MPP > PP > 8-MOP dans la partie lineaire de la courbe d'induction, et 8-MOP > PP > MPP au niveau maximum de SCE obtenu. L'application topique de 15 g par cm 2 de psoralenes chez les souris albinos 17NCZ produit apres 115 irradiations par les UVA (1,18 J/cm 2 ): 80% de tumeurs avec le 8-MOP, 56% de tumeurs avec le MPP et 39% avec le PP, en 21 mois. Chez l'homme, 2 heures apres l'application topique de 10 g/cm 2 la MED est de 20 J/cm 2 d'UVA. L'application de 8-MOP, MPP et PP sur differentes zones des memes plaques psoriasiques, a la meme concentration molaire, suivie, 2 heures apres, de l'irradiation par la meme dose d'UVA, montre une efficacite therapeutique legerement plus elevee avec les pyrido-psoralenes qu'avec le 8-MOP. MPP et PP ne sont que peu pigmentogenes. En conclusion, MPP et PP peuvent augmenter la securite et l'efficacite de la PUVA therapie.

The synthesis of 15 compounds related either to the benz[c]acridine or to the benz[a]acridine series is reported. Spectral data, i.e., NMR and EI fragmentation, are given. These compounds were tested for carcinogenic activity in mice of the XVIInc/Z strain by subcutaneous injection. Only three weak carcinogens were detected, 5,6-dihydro-5,6-dihydroxy-12-methylbenz[a]acridine, 3-methoxy-7-methylbenz[c]acridine, and 4-acetoxy-7-methylbenz[c]acridine. These results are discussed with consideration to the data previously obtained with other benzacridines and condensed quinolines.

Dibenzo[a,e]fluoranthene is treated by osmium tetroxide, the nature, structure, and configuration of the compound obtained (a trans dihydro diol) are defined taking into account the chemical, theoretical, and physicochemical arguments.

SummaryDaily subcutaneous administration of concentrated preparations of crude or highly purified mouse brain interferon inhibited the multiplication of Friend virus and the development of splenomegaly in Swiss mice. Initiation of a continued interferon treatment 1 week after viral inoculation, at a time when splenic enlargement had already developed, still exerted a significant inhibitory effect on further development of splenomegaly. Interferon administration for only the 1st week after viral infection was ultimately ineffective. On histologic examination, far fewer foci of Friend cells were observed in the spleens of interferon treated mice than in the spleens of untreated mice. It was suggested that the inhibition of splenomegaly observed after repeated interferon administration was due to a continued inhibition of viral multiplication. Further evidence was presented that interferon itself was responsible for the inhibitory effects observed.

Polyploidy occurs through a series of cellular divisions of particular types, the first of which is the formation of binuclear cells. Therefore the liver of an animal must be in a state of growth for polyploid cells to be formed. It is possible to prevent polyploid hepatocytes from appearing by bringing about in young animals either a hypophysis insufficiency or a protein deficiency large enough to stop the development of the animal. The lack of growth inhibits the formation of polyploid cells even if the growth hormone is given by injection. The factors inducing the formation of polyploid cells should therefore be tested by their action on hepatic cell multiplication in baby rats (three weeks old or less) which normally show very few binuclear or polyploid cells.

Theoriquement, il existe 12 derives monoalkyles et 66 derives dialkyles du benzo (a) pyrene correspondant a un groupement alkyle determine, pour neparler que des substituants les plus simples. The carcinogenicity of 14 mono-, di-, and trimethylated benzo(a)pyrenes has been investigated. The majority exhibit highly pronounced sarcomagenic properties both with regard to the percentage of animals producing tumours, and to the latency period. Many of these homologues are distinctly more active than the non-substituted benzo(a)pyrene. Comparison of these experimental results with the theoretical calculations of the electronic charge of the K-zone, together with the determination of the electronegativities of K-zone complexes, shows a satisfactory correlation. It can be predicted that the introduction of more than three methyl groups into the molecule ofbenzo(a)pyrene will probably lead to the loss of carcinogenicity. Resume On a determine les proprietes cancerogenes de 14 homologues mono- ou polymethyles du benzo(a)pyrene. La plupart de ces composes exercent des proprietes sarcomogenes extrěmement prononcees, tant au point du vue du pourcentage des animaux cancerises que du temps de latence. Plusieurs de ces composes sont nettement plus actifs que le benzo(a)pyrene non-substitue. La confrontation des resultats experimentaux avec les calculs de la charge electronique de la zone K, completee par l'etude de l'electronegativite des complexes de cette zone, montre l'existence D'UNE correlation satisfaisante. On peut prevoir que L'introduction de plus de trois groupements methyle dans la molecule du benzo(a)pyrene devrait conduire a la perte de toute activite cancerogene.

BY immunological techniques, Darcy1 has shown, in rats bearing a Walker's tumour, the appearance of a serum protein absent in normal rat serum.

43 heteropolycyclic compounds belonging to a homologous series were investigated for mutagenicity. The results are compared with carcinogenicity data obtained with the same batches of compounds under conditions identical for all of them. Mutagenicity was tested in the Ames test with Salmonella typhimurium strains TA1535, TA1537, TA98 and TA100 in the presence and absence of liver 10 000 g supernatant from rats treated with Aroclor 1254. Carcinogenicity was tested by injection of the compounds into subcutaneous tissue of XVIInc/Z mice. 18 test compounds showed carcinogenic activity, some strongly, others only weakly. Of these, 17 were detected as mutagens: one weak carcinogen did not revert the Salmonella strains. No quantitative correlation was observed between the extents of the mutagenic and the carcinogenic effects. Of the 25 substances that did not produce tumours, 13 showed mutagenicity (12 in the presence, 2 in the absence, of the liver homogenate). The mutagenic effects of these compounds were quantitatively similar to those of the compounds that produced tumours. The most sensitive strain of Salmonella typhimurium was TA100. It detected all 30 mutagens. TA98 was mutated by 25 compounds, TA1537 by 16 compounds. No mutagenic effects were seen with TA1535. Possible reasons for the high percentage of apparently “false positives” in the Ames test and the lack of a quantitative correlation between the potency of the mutagenic and carcinogenic effects are discussed. It is suggested that the complexity of the metabolism of these heterocyclic compounds may lead to critical differences in metabolism in mouse subcutaneous tissue in vivo and in liver homogenates from rats treated with Aroclor. Therefore the present study will be extended to life-long oral and intrahepatic carcinogenicity tests leading to a higher proportion of metabolism in the liver.

Dibenzo[a,e]fluoranthene is treated by osmium tetroxide, the nature, structure, and configuration of the compound obtained (a trans dihydro diol) are defined taking into account the chemical, theor...

When the MLg Mouse cells were treated with the chemical carcinogens, in the presence of microsomal enzymes and NADPH2 after 5-iododeoxyuridine (IUdR) treatment, the induction frequency of the endogenous C-type virus was increased by nearly 10-fold in comparison with the cultures treated with IUdR only. In the preliminary screening of several polycyclic hydrocarbons including carcinogenic and non-carcinogenic products, apparently there was no correlation between the carcinogenecity in vivo and the stimulation capacity of IUdR induced C-type virus activation in our test conditions.

The synthesis of 15 compounds related either to the benz[c]acridine or to the benz[a]acridine series is reported. Spectral data, i.e., NMR and EI fragmentation, are given. These compounds were tested for carcinogenic activity in mice of the XVIInc/Z strain by subcutaneous injection. Only three weak carcinogens were detected, 5,6-dihydro-5,6-dihydroxy-12-methylbenz[a]acridine, 3-methoxy-7-methylbenz[c]acridine, and 4-acetoxy-7-methylbenz[c]acridine. These results are discussed with consideration to the data previously obtained with other benzacridines and condensed quinolines.

The net total uptake of several amino acids at low (0.8-3.1 mumoles/liter) as well as high (800-1200 mumoles/liter) extracellular concentrations, by normal rat liver, a premalignant liver, a solid hepatoma, and the Zajdela ascitic hepatoma cells, has been compared under conditions in which protein synthesis continues. At low amino acid concentrations, the initial (3 min) total uptake of the various amino acids in the Zajdela cells, was 3-10 (average 7) times more, and the intracellular concentration of the labeled amino acids taken up 14-45 (average 31) times more, than in normal liver. At the high amino acid concentrations, the total uptake in the Zajdela cells, at 60-120 min was 2-5 (average 3.5) times more, and the intracellular concentration of the amino acids taken up 8-18 (average 13) times more, than in normal liver; the corresponding values for the premalignant liver and the solid hepatoma were in between those for normal liver and the Zajdela cells. Further, the rate of the total uptake of amino acids, their intracellular concentration, the proportion of the amino acid taken up utilized for protein synthesis, the rate of incorporation of the amino acid taken up into protein, and the cellular growth rate, seemed to be correlated in the four cell/tissue preparations studied. In most cases, the rate of the net uptake fell drastically with time, the uptake virtually stopping after 90-180 min, probably due to lack of serum in the incubation medium.

Stimulation of liver cell multiplication was obtained under two different experimental conditions. 1 A single injection of casein solution resulted in (a) an identical synchronized mitotic wave response in 10-day old male and female rats and (b) a significantly lower response in adult male rats compared to females, a difference which was reduced by castration of males at birth but essentially maintained if animals were operated when 10 days old. 2 Partial hepatectomy shortly after puberty resulted in active hepatocyte multiplication occurring 3 hr earlier in females than in males. This difference was suppressed when females were ovariectomized at birth and significantly reduced when they were spayed at a later age. Hepatocytes of castrated females entered actively into S phase 2 hr later than the sham-operated controls. Unilateral ovariectomy on the other hand indicated that during compensatory and/or hyper-compensatory activity of the single ovary there was a maximum difference between the male and female rate of [3H]thymidine uptake in liver nuclei 20 hr after hepatectomy. A further kinetic study (t= 25, 30, 40, 65, 90 hr) indicated no significant sex-related difference in the number of S phases per 10,000 cells. The DNA content of regenerating versus control livers was comparable in both sexes at t= 22 and 90 hr but higher in females at t= 40 and 65 hr. A possible early postnatal interference of certain hormonal mechanisms in the receptivity to mitotic stimuli is postulated and discussed.

Inhibition of the G1-S transition in synchronized baby rat hepatocytes was obtained by a subcutaneous injection of adult rat liver cytosol. This inhibitory activity was observed only with liver cytosol and not with kidney or spleen cytosol. The liver cell was a relatively specific target: no modifications were recorded in the kidney or submaxillary gland and inconsistant variations were found with tongue epithelium. The activity was associated with a non-dialysable factor. Physiological investigations support the opinion that the liver factor is the origin of the serum factor which had previously been described. Both factors were absent during the first three weeks of life. They appeared together during the 4th week in correlation with a decreasing rate of liver cell multiplication and then reached progressively their definitive adult levels. After 2/3 hepatectomy in adults, the liver cytosol retained its inhibitory activity, but the serum factor was reversibly neutralized by an antagonistic factor. Both inhibitory factors could be prematurely induced in baby rats and appeared transiently during the period of low mitotic activity following a wave of synchronized liver cells generated by an irritating stress. This inhibitory system is characteristic of the last developmental stages of the liver when growth decelerates before reaching a steady state. It seems to reduce the multiplication of hepatocytes by decreasing their sensitivity to stimuli initiating cell replication.

A short review of pathogenic factors in U.V. light skin carcinogenesis in the mouse is presented. Caffeine and theophylline applied locally during U.V. irradiation caused a 50 percent reduction of skin tumour induction in Swiss mice. These two chemicals are inhibitors of DNA postreplication repair, but they also raise the intracellular level of cyclic AMP by inhibiting cAMP phosphodiesterase with, as a consequence, a possible slowing down of cellular growth. Control experiments using three different chemicals capable of raising the cAMP level in epidermal cells gave negative results. These experimental data are compatible with our original hypothesis according to which production of skin cancers by U.V. radiation is in same way related to DNA repair which helps the cell to survive but allows or favours the occurrence of errors in cellular DNA.

Zajdela ascitic hepatoma cells are shown to take up pyrimidine bases at much lower rates than obtained in slices from normal rat liver. The rates of uptake of adenine and uridine by the Zajdela cells are, however, as high as in the slices. Like the slices, again, the Zajdela cells take up E. coli RNA and DNA at very low rates but, unlike the slices, thses cells degrade rapidly the RNA taken up. The Zajdela cells resemble parenchymal cell suspensions derived from normal rat liver in regard to the uptake of pyrimidine bases and the ability to degrade heterologous RNA.

SUMMARY The carcinogenic risk of photochemotherapy (PUVA) with bi-functional furocoumarins such as 8-methoxypsoralen (8-MOP) which form cross-links in cellular DNA has initiated a search for active but less hazardous psoralens. A new compound, 3-carbethoxypsoralen (3-CPs), studied in the yeast Saccharomyces cerevisiae (eukaryote), has been shown to be very photoactive on DNA and to form only mono-additions to DNA. These lesions appear to be more easily repaired than the cross-links induced by 8-MOP. 3-CPs produces less nuclear genetic events such as nuclear mutations and mitotic crossovers, but more cytoplasmic ‘petite’ mutations (damage to mitochondrial DNA) than 8-MOP. In mice it was demonstrated that after local or intra-peritoneal administration, in contrast to 8-MOP. 3-CPs is non-toxic, non-erythematogenic, and non-carcinogenic. A study of ten psoriatic patients has shown that local applications of 3-CPs plus UV-A exhibit about the same therapeutic activity for the clearing of psoriatic lesions as local treatment with 8-MOP plus UV-A, but without any localized hyperpigmentation.

When mouse MLg cells were treated with 3-methylcholanthrene or 7,12-dimethylbenz[alpha]anthracene in the presence of microsomal enzymes and NADPH after 5-iododeoxyuridine (IUDR) treatment, the induction rate of the endogenous C-type virus was increased fivefold to sixfold in comparison with the culture treated with IUDR only. In this reaction, both the microsomal enzymes and NADPH were indispensable. 7,8-Benzoflavone, an inhibitor of the metabolism of hydrocarbons in hamster embryo cultures, inhibited the reaction. For detecting the enhancing activity, the concentration of IUDR for the pretreatment, the concentration of the test products, and the duration of the treatment with the products were important factors. In screening 30 polycyclic hydrocarbons, we were unable to detect a correlation between the in vivo carcinogenicity in the skin and the enhancing activity in the conditions tested.

Dibenzo(a,e)fluoranthene (DBF), a highly carcinogenic polycyclic hydrocarbon without an apparent K-region, binds covalently to DNA, transfer RNA, and polyribonucleotides when incubated with hepatic microsomal fractions under standard conditions. Optimal binding conditions for [3H]DBF were established. Methylcholanthrene-pretreated mouse liver microsomes induced a higher level of binding of [3H]DBF to DNA than did similarly induced rat liver microsomes. 7,8-Benzoflavone strongly inhibited the binding of this polycyclic aromatic hydrocarbon to DNA, while cyclohexene oxide and trichloropropene oxide had an enhancing effect when used in the presence of rat liver microsomes. An unexpected inhibitory effect was observed with cyclohexene oxide in mouse liver microsome-enriched medium. [3H]DBF bound twice as much to denatured as to native DNA. Incubation of [3H]DBF in the presence of liver microsomes and polyribonucleotides (polyadenylate, polyuridylate, polyguanylate, and polyinosinate) indicated that binding occurs mainly with guanine. Binding of [3H]DBF to DNA of various origins was found to be directly proportional to the amount of GC pairs. Preliminary results indicate a covalent bond between DBF and nucleic acids.

Repeated s.c. administration of chloroethylene oxide, a reactive metabolite of the carcinogen vinyl chloride, induced local tumors in mice, with an incidence comparable to that of bis(chloromethyl)ether, a structurally related human and animal carcinogen, when both compounds were applied at maximum tolerated chronically toxic doses; no tumors distant from the injection site were produced. Bis(chloromethyl)ether, chloroethylene oxide, and its rearrangement product chloroacetaldehyde, a highly toxic compound, were further tested in an initiation-promotion experiment. Application to the skin of a single dose of either bis(chloromethyl)ether or chloroethylene oxide, followed by 3-times-weekly applications of 12-O-n-tetradecanoylphorbol-13-acetate for 42 weeks, produced skin tumors in mice; chloroacetaldehyde under comparable conditions produced no increase in benign or malignant tumors. A good correlation between the chemical reactivity, on the basis of hydrolysis constants in aqueous media, and the carcinogenicity of the three compounds was noted. Our results support the hypothesis that epoxidation of the thylenic double bond in vinyl chloride yields an ultimate carcinogenic metabolite, chloroethylene oxide, a highly reactive compound which appears also to be largely responsible for the known genetic changes caused by the parent compound.

The induction of skin cancer in mice of the Swiss (Carshalton) strain, by repeated irradiation with UV-light, was strikingly reduced by the local application of caffeine prior to each exposure. Theophylline displayed the same activity. These two substances have been selected as probable inhibitors of error-prone, postreplicative DNA repair. Conversely, reductone and chloroquine, which are considered as inhibitors of the error-free, prereplicative excision repair, did not modify the incidence of the tumors. Special emphasis has been given to the histologic behavior of radiolabeled caffeine in the normal and UV-irradiated epidermis of the mouse in vivo and to the ability of mouse epidermal cells in vitro to repair DNA after UV irradiation.

The fluorescence increase, due to NAD(P) reduction, following microelectrophoretic injection of glucose 6-P (G6P) into EL2 and NCTC 8739 single living cells treated with diBenzo(ae)Fluoranthene (diB(ae)F) and non-treated, has been studied with a rapid microspectrofluorometer. This study shows the enhanced capacity of treated cells to utilize larger doses (6–10 times more) of G6P than control cells. The time course of the return to the initial fluorescence level is essentially related to the magnitude of the injection dose. There are alterations (e.g. red & blue shifts) in the fluorescence spectrum of diB(ae)F-treated cells before injection and in the increase spectrum after injection of G6P, as compared to the same spectra in the diB(ae)F-untreated cells. This is discussed in reference to the metabolization of diB(ae)F as an alternative pathway for the reoxidation of NAD(P)H.

Cells of the hybrid clone M (Barski) in culture are distinguished by functional properties which in part are derived from two different parental strains. The cells show a wide range of ploidy. Their nucleoli occur singly or in multiples and have diameters sufficiently large to permit autoradiographic resolution between labelled nucleoli and labelled extranucleolar chromatin. Tritiated cytidine and uridine were used for studying the significance of varying patterns of nuclear RNA labeling in single cells and in cell-pairs. The results indicate

1,12-Diazadibenzo(a,i)pyrene (I), an isostere of the extremely potent carcinogen dibenzo(a,i)pyrene, also displays carcinogenicity although to a considerably lesser degree than the latter compound. While dibenzo(a,h)pyrene is known to be distinctly less active than dibenzo(a,i)pyrene, surprisingly 4,11-diazadibenzo(a,h)pyrene (II) shows a greater activity than I. Another hexacyclic diaza-hydrocarbon, 4,12-diazadibenzo(g,p)chrysene (III), which is devoid of a meso-phenanthrenic region, proved totally inactive.