Croissance individuelle et dynamique de population de Daphnia Magna en culture dans les eaux usées traitées

Résumé Pour atteindre les buts visés par le recyclage biologique des eaux usées, il faut exploiter une population d'organismes filtreurs dont l'augmentation nette de biomasse est rapide et importante. L'augmentation nette de biomasse sera favorisée par une croissance individuelle, une reproduction et une survie excellentes dans l'eau usée traitée. L'étude de ces paramèters sur des cohortes de Daphnia magna soumises à différentes conditions expérimentales, indique qu'il s'agit d'un organisme prometteur pour le recyclage biologique. Dans nos conditions expérimentales, D. magna montre un bilan azoté positif durant toute sa vie. La production rapide de biomasse est favorisée par une température élevée (15 °C) et une nourriture abondante. L'eau traité montre les signes d'une certaine toxicité envers les juvéniles mais non envers les adultes. Nos données établissent que la production d'oeufs requiert une taille minimale de la femelle de 2,7 mm, information primordiale pour l'exploitation future de la population.

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To realize the objectives of the biological recycling of wastewaters, it is necessary to exploit a population of filtering organisms, the biomass of which shows a rapid and important net increase. The net increase of biomass is favored by excellent individual growth, reproduction and survival in treated wastewaters. The study of these parameters, with cohorts of Daphnia magna submitted to different treatments, indicated that it is a promising organism for biological recycling. Under our experimental conditions, D. magna exhibited a positive nitrogen balance for the whole of its life. The rapid production of biomass was favored by high temperature (15 °C) and abundant food. The treated wastewaters proved to be somewhat toxic to juveniles but not to adults. Our results demonstrated that the egg production requires a female minimal size of 2.7 mm; this information is most important in the future exploitation of the population.

     

Retrograde Inhibition of Transmitter Release by ATP

Abstract: After labelling ACh tissue stores in Torpedo electric organ prisms with radioactive acetate, the release of ACh and ATP triggered by electrical stimulation or KCI depolarization was measured in the same perfusate samples. The luciferin-luciferase reaction for ATP was first counted, then the radioactive content of the sample determined. Further evidence showing that ATP release resulted from postsynaptic transmitter action was that carbachol could induce the release of ATP. A dose-response curve was obtained. Curare or α-bungarotoxin block the release of ATP elicited by carbachol. When triggered by KCI depolarization the increased efflux of ACh and ATP returned to low levels in spite of the maintained depolarization. After two successive KCI depolarizations, it was possible to dissociate the release of both substances. The efflux of ATP was exhausted while ACh release was maintained. If the second KCI depolarization was delayed ATP release recovered, but the release kinetics of ACh and ATP were sustained. The exhaustion of endogenous ATP release or the action of exogenous ATP had little or no effect on the release of ACh triggered by KCI depolarization. On the contrary, the release of ACh induced by electrical stimulation was sensitive to the action of adenine nucleotides, and a quantitative estimation of the inhibition of ACh release by ATP and adenosine could be made. At the onset of stimulation ATP release predominated, being gradually replaced by adenosine, which can be reuptaken. This would terminate the inhibitory action of the nucleotide. Carbachol inhibits evoked ACh release, while the effect of α-bungarotoxin was to increase spontaneous ACh release. These effects could be respectively mediated by an increased or a reduced release of ATP resulting from the postsynaptic action of ACh agonists or antagonists. However, a direct presynaptic effect of these substances is not excluded. It seems possible that the action of ATP on ACh release can be explained through its inhibition of the depolarization-evoked Ca²⁺ entry.     

Synaptosomal uptake

Using purified synaptosomal preparations from rat brain, the uptake ofl-tryptophan and norepinephrine was studied. We were unable to replicate some of the results of the experiments obtained with crude mitochondrial, fractions (P₂). Thus we examined the validity of the results of uptake studies obtained with the crude synaptosomes and established conditions which would simulate the biochemical milieu in which the nerve terminals functionin vivo, such as active substrate-dependent respiration, respiratory coupling on addition of ADP, low impurity of noncharacteristic markers, exogenous added proteins (e.g. bovine serum albumin), and verification by electron microscopy. All uptake studies withl-TRP and NE were completed in a system designed for simultaneous recording of respiration and the effect of added ADP. This system was also employed in comparative studies with mitochondria purified by multiple density gradients derived either from the perikaryon or from synaptosomes. Synaptosomal or mitochondrial preparations which did not conform to the above criteria invariably showed significantly lowered ability of uptake ofl-TRP or NE. This was found to be related to impairment in their respiratory and coupling ability. When the experimental conditions of others were employed, the time course of uptake of TRP for crude synaptosomes (P₂) was 100 nmol/g/min and was linear for 2.5 min, while for the purified synaptosomes it was 20 nmol/g/min with a l-min linearity. The mitochondria purified from P₂ displayed 30 nmol/g/min uptake withl-TRP with a linearity of 2.5 min. Reconstituted system of purified synaptosomes and mitochondria gave 60 nmol/g/min ofl-TRP transport with 2.5 min linearity. Also examined was the effect of eight different media. It was found that Krebs-Ringer solution containing glucose (40 mM), pyruvate and malate (10 mM), and ADP (250 nmol) gave optimal uptake of TRP both for synaptosomes and for mitochondria, increasing it to 60 and 86 nmol/g/min. The above conditions also enhanced the uptake of NE by synaptosomes and mitochondria. Uptake of NE was not proportional to protein concentration when the protein content exceeded 0.4 mg. Purified synaptosomal mitochondria accumulated NE more actively than the purified nonsynaptic free mitochondria, albeit at the same rate. Synaptic and free mitochondria had an impaired uptake of NE in presence of DNP, antimycin A, and rotenone, and unlike withl-TRP, pyruvate and malate also reduced uptake of NE. Significant differences were noted for the cytochrome oxidase activity between the synaptosomal and free michondria when compared to that of the homogenate.     

The pineal gland of the mole-rat (Spalax ehrenbergi,Nehring)

Summary A comparative investigation of the distribution of monoaminergic neurons in non-malacostracan crustaceans was performed with the histochemical fluorescence method of Falck-Hillarp.Two fluorophores were found: the more widespread of the two emits a green fluorescence; and the more sparsely distributed emits a yellow to brown-yellow fluorescence.Specific green fluorescent areas were shown to exist in the protocerebrum. The central body and the optic ganglia of the compound eye (where present) are always fluorescent. Moreover, the centre of the nauplius eye may have a green fluorophore, as in ostracods, and a neuropile area, here called the frontal area. These neuropile centres are known from ordinary histological studies of the nervous system. In addition, there are specific monoaminergic centres, such as the so-called dorsal area of phyllopods and anostracans as well as the copepod specific areas. Specific monoaminergic areas appear in the deutocerebrum and the suboesophageal ganglion where they are particularly well developed.Presumed sensory neurons in the cavity receptor organ of Artemia salina are shown to be monoaminergic. Monoaminergic sensory neurons have not been described previously in Arthropods.Presumed motor innervation of hind-gut and trunk muscles is also found, and it is concluded that in crustaceans neurons of every type (sensory, internuncial, motor) may be monoaminergic.We have enjoyed unrestricted laboratory facilities at the Department of Histology, Faculty of Medicine, and with great pleasure express our sincere thanks to Prof. Bengt Falck. — Grants from the Swedish Natural Science Research Council (2760-007), the Swedish Medical Research Council (04X-712), the Royal Swedish Academy of Science (Hierta-Retzius), the Royal Physiographic Society of Lund, and the University of Lund supported the work.     

Effect of arginine deficiency on the reproduction of human cytomegalovirus.

In arginine-deprived human embryonic fibroblasts the reproduction cycle of human cytomegalovirus (CMV) is incomplete. Infectious virus cannot be demonstrated in cell disintergrates, and from among the CMV antigens only the diffuse cytoplasmic antigen is detectable by immunofluorescence. The antigens localized in the cell membrane and those appearing during the complete cycle as large granules or inclusion-like bodies in the nucleus do not appear in the absence of arginine. The CMV genome persists in the arginine-deprived culture; after re-feeding with arginine-containing medium, maturation of virions soon ensues. Maturation could be prevented by inhibitors of protein synthesis, but not by DNA inhibitors, added simultaneously with completion of the medium.     

Division of labor within the DNA damage tolerance system reveals non-epistatic and clinically actionable targets for precision cancer medicine

Crosslink repair depends on the Fanconi anemia pathway and translesion synthesis polymerases that replicate over unhooked crosslinks. Translesion synthesis is regulated via ubiquitination of PCNA, and independently via translesion synthesis polymerase REV1. The division of labor between PCNA-ubiquitination and REV1 in interstrand crosslink repair is unclear. Inhibition of either of these pathways has been proposed as a strategy to increase cytotoxicity of platinating agents in cancer treatment. Here, we defined the importance of PCNA-ubiquitination and REV1 for DNA in mammalian ICL repair. In mice, loss of PCNA-ubiquitination, but not REV1, resulted in germ cell defects and hypersensitivity to cisplatin. Loss of PCNA-ubiquitination, but not REV1 sensitized mammalian cancer cell lines to cisplatin. We identify polymerase Kappa as essential in tolerating DNA damage-induced lesions, in particular cisplatin lesions. Polk-deficient tumors were controlled by cisplatin treatment and it significantly delayed tumor outgrowth and increased overall survival of tumor bearing mice. Our results indicate that PCNA-ubiquitination and REV1 play distinct roles in DNA damage tolerance. Moreover, our results highlight POLK as a critical TLS polymerase in tolerating multiple genotoxic lesions, including cisplatin lesions. The relative frequent loss of Polk in cancers indicates an exploitable vulnerability for precision cancer medicine.