Inhibition of DNA synthesis in relation to enhanced survival of UV-damaged herpes virus in monkey cells treated by a variety of 2-nitronaphthofurans

Various 2-nitronaphthofuran derivatives (related to each other by simple structural modifications) were tested for 2 different effects in CV-1 monkey kidney cell cultures: the immediate inhibition of normal DNA synthesis and the capacity of pretreated cultures (40 h of contact) to support the replication of UV-damaged Herpes simplex virus (HSV). For all compounds tested, a fair correlation was found between their efficiencies to inhibit cellular DNA synthesis and to provoke an increase in UV-HSV production (virus reactivation). Virus reactivation was due to an increase in both the number of virus-producing cells and the amount of infectious particles produced per cell. The most efficient 2-nitronaphthofurans (particularly 2-nitro-7-methoxy-naphtho[2,1-b]furan-R 7000) were at least as potent as aflatoxin B1 in inducing virus reactivation.     

Effects of essential divalent metals on carcinogenicity and metabolism of nickel and cadmium

Interactions between the physiologically essential metals calcium, magnesium, and zinc and the carcinogenic metals nickel and cadmium were investigated to help elucidate the mechanisms of action of the carcinogenic metals. Bioassay studies revealed several significant findings, including: (1) the ability of magnesium and calcium to inhibit nickel-induced elevation of pulmonary adenoma incidence in strain A mice; (2) the ability of magnesium, but not of calcium, to prevent cadmium-induced subcutaneous sarcoma formation; and (3) the ability of magnesium, but not of calcium, to inhibit nickel-induced muscle tumor formation. Biochemical studies indicated a direct relationship between the antitumorigenic potential of magnesium and the capacity of this metal to: (1) inhibit nickel and cadmium uptake by the target tissues in vivo; (2) inhibit nickel-induced disturbances in DNA synthesis in vivo; (3) inhibit nuclear and cytosolic uptake of nickel by the target tissue cells in vivo; and (4) inhibit nickel and cadmium binding to DNA in vitro. Calcium, which in most cases did not prevent carcinogenesis, had no consistent influence on the uptake of carcinogenic metals or their biochemical effects in the target tissues. Magnesium and zinc, but not calcium, were also found to attenuate the acute toxic effects of nickel, indicating a possible correlation between prevention of acute effects and reduction in tumorigenicity. Zinc, which antagonizes cadmium tumorigenicity in the rat testis, was found to reduce markedly cadmium uptake into isolated testicular interstitial cells. Also, zinc was found to inhibit strongly cadmium binding to DNA in vitro.     

Nitrogen mineralization ofSesbania sesban used as green manure for lowland rice in Sri Lanka

Sesbania sesban was evaluated as green manure crop for lowland rice in the Dry Zone of Sri Lanka. The legume was grown during a fallow period before lowland rice (Oryza sativa) and ploughed under just before transplanting. Weight loss and nitrogen content in litterbags containing leaves, stems and roots of the legume were monitored. Comparisons were made between rice yields from 20 m² plots after green manuring in combination with different nitrogen fertilizer levels (0, 2.4, 4.8 and 7.2 gm⁻²) and nitrogen fertilizer (9.6 gm⁻²) alone. Above-ground biomass ofS. sesban was 440 gm⁻² (dry wt) when ploughed under after 84 days growth. N-content in leaves, stems and roots was 3.76%, 0.41% and 0.73%, respectively. This gave a N-input fromS. sesban of 9.2 gm⁻² (8.3 g from above-ground parts and 0.9 g from roots). The corresponding K and P inputs were 7.3 and 0.6 gm⁻² respectively. The nitrogen rich leaves, which contained 88% of the nitrogen in the above-ground parts, decomposed and released its nitrogen much more rapidly than the stems and roots. After only four days the leaves had released 5.3 g Nm⁻² and after 14 days they had released 6.4 g Nm⁻². The highest rice yield (505 gm⁻²) was obtained usingS. sesban and 4.8 gm⁻² of N-fertilizer. The yields with only N-fertilizer or onlyS. sesban were 442 gm⁻² and 396 gm⁻², respectively. Due to the rapid decomposition of the nitrogen rich leaves,S. sesban did not behave as a slow release fertilizer. Thus, it is not necessary to apply nitrogen fertilizers as a basal dose.     

Hybridization of DNA from methanogenic bacteria with nitrogenase structural genes (nifHDK)

Summary Using the Southern hybridization technique, homologies were examined between restricted DNA of four methanogenic bacteria (Methanobacterium ivanovi, Methanobacterium thermoautotrophicum, Methanococcus voltae, Methanosarcina barkeri) and the nif (nitrogen fixation) genes of Klebsiella pneumoniae and Anabaena strain 7120. With K. pneumoniae probes, no hybridization was observed with nifA, nifNE, and nifJ but positive results were obtained with the nifHDK genes coding for nitrogenase. Homology was detected, in the four strains, with K. pneumoniae and Anabaena nifH probes. In M. voltae and M. ivanovi, the homology found with nifH was estimated to be about 70% and a weaker hybridization was observed also with nifD and nifK. In M. voltae, the sequence homologous to nifH was found on a 3.0 kbp HindIII fragment and sequences homologous to nifD and nifK on a 3.8 kbp HindIII fragment. The 3.0 kbp fragment was cloned and the region homologous to nifH was localized more precisely. When this fragment was used as a probe against other DNAs, it behaved as a K. pneumoniae and Anabaena nifH probe. The results suggest that the structural genes for nitrogenase may be present in archaebacteria and raise interesting questions regarding their evolution.     

Les supports morphologiques de l'intégration dans la colonie de Veretillum cynomorium Pall. (Cnidaria,Penntularia)

The morphological supports of integration, including the nervous system, are to be found.After a morphological observation, ecto and endoderms and their intercellular junctions are presented.The regionally different mesogleal synaptic nerve nets are surrounded by ecto and endodermal nervous structures.The presence of behavioural activity centers is also discussed.

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Liste des abréviations des figures AS autozoïde sectionné - AU autozoïde - CAL canal longitudinal - CAV cavité gastrique - CC corps compact - CGL cellule globuleuse myo-épitheliale MESlame mésentériale MF microfilament - CGR cellule granuleuse myo-épithéliale - CLC cloison commune à deux autozoïdes - CLR cloison radiale - CLT cloison transversale - CM corps myélinique - CME cellule mesenchymateuse - CNE cellule nerveuse ectodermique - CNEN cellule nerveuse endodermique - CNM cellule nerveuse mésogléenne - COL colonne - CSP cellule spumeuse - CSPH cellule sphéruleuse - CU cellule urticante - D dépot de matériel intercellulaire (zonula adhaerens) - DS desmosome septé - ECT ectoderme - EE empilement d'ergastoplasme rappelant un corps de Nissl - FF fibres fasciculées h structure - G glycogène - GA granule aréolé - IC inclusion crênelée - M mitochondrie - MB membrane basale - ME mésoglée - MES lame mésentériale - MF microfilament - MT figure interprétée on terme de microtubule - MV microvilli - N noyau - E neurite - NO nodosité - P pédoncule - PC paroi des canaux - PE perforation - R rachis - SF siphonozoïde fendu - SIPH siphonozoïde - SM sipment musculaire d'une cellule myoépithéliale - T travé ous-siphonozoïdale - TME travée mésogléenne - VC vésicule claire - VME vésicule mésenchymateuse - ZI zône intermédiaire - I synapse polarisée - 2 synapse réciproque - 3 figure ressemblant à un desmosome septé - 4 contact par apposition Cc travail correspond à la première partie d'une thèse de Doctorat d'Etat, consacrée aux «Structures et aux mécanismes de l'intégration dans la colonie de Veretillum cynomoriurra» — Il a été effectué au sein de l'Equipe de Recherche Associée au C.N.R.S., n°183 (Directeur Al. Pavans de Ceccatty) avec le concours du Laboratoire Arago à Banyuls sur Mer (France) et la collaboration technique de Madame J. Villeneuve.     

Structural Aspects of Saltatory Particle Movement

A variety of cells possess particles which show movements statistically different from Brownian movements. They are characterized by discontinuous jumps of 2–30 µ at velocities of 0.5–5 µ/sec or more. A detailed analysis of these saltatory, jumplike movements makes it most likely that they are caused by transmission of force to the particles by a fiber system in the cell outside of the particle itself. Work with isolated droplets of cytoplasm from algae demonstrates a set of fibers involved in both cytoplasmic streaming and saltatory motion, suggesting that both phenomena are related to the same force-generating set of fibers. Analysis of a variety of systems in which streaming and/or saltatory movement occurs reveals two types of fiber systems spatially correlated with the movement, microtubules and 50 A microfilaments. The fibers in Nitella (alga) are of the microfilament type. In other systems (melanocyte processes, mitotic apparatus, nerve axons) microtubules occur. A suggestion is made, based on work on cilia, that a microtubule-microfilament complex may be present in those cases in which only microtubules appear to be present, with the microfilament closely associated with or buried in the microtubule wall. If so, then microfilaments, structurally similar to smooth muscle filaments, may be a force-generating element in a very wide variety of saltatory and streaming phenomena.