Resumption of cellular activity induced by cytokinin and gibberellin treatments in tomato flowers targeted for abortion in unfavorable light conditions

Mitotic activity and nuclear DNA synthesis in tomato ( Lycopersicon esculentum Mill., cv. King plus) flowers targeted for abortion under unfavorable light conditions are completely stopped 6 days after macroscopic appearance of the inflorescence. Ovular cells are arrested at the G₁ (80%) and G₂ (20%) stages of the cell cycle. Exogenous applications of a mixture of N⁶-benzyladenine (BA) and gibberellins A₄₊₇ (GA) directly on the inflorescence may prevent its failure. Nuclear DNA synthesis and mitoses resume in ovules of the flower 16 to 20 h after the BA+GA treatment. When applied alone, BA and GA are able to mimic the effect of the mixture upon the progression of ovular cells through their cycle. Sporogenesis processes are also set in motion by the exogenous plant growth regulators. The mechanism of action of cytokinins and gibberellins in the control of floral development is discussed.     

Synthesis and phosphorylation of cytoskeleton components in foetal,regenerating and adult normal rat hepatocytes during culture

Summary Detergent insoluble material (DIM) was prepared by gentle treatment with detergent from foetal, regenerating and adult normal rat hepatocytes cultured for various times. It retained to some degree the morphology of the cells. After incubation of intact cells with ³⁵S-methionine, most of the labelled DIM proteins were found to be components of the cytoskeleton. They included several cytokeratins, vimentin and actin. The synthesis rate varied with the age of animals and culture conditions. The high synthetic rate of vimentin in foetal and regenerating hepatocytes could be associated with cell proliferation. No correlation was found between cytokeratin synthesis and hepatocyte growth. Most of the cytoskeleton proteins could be phosphorylated in intact cells and in DIM from cultured hepatocytes. However the degree of phosphorylation of these proteins was not related to their synthetic rate. The decreased phosphorylation level in cultured adult rat hepatocytes could be related to the rapid loss of specific functions.     

Isolation of microorganisms on 3-butyn-1-ol and other acetylenic compounds

The microbial potential to degrade acetylenic compounds (alkynes) was investigated, and several fungi and bacteria were isolated on 2-propyn-1-ol, 3-butyn-1-ol, propynoic acid, and 2-butyne-1,4-diol. The results indicate that a wide variety of microorganisms may degrade alkynes in nature.     

Concanavalin A-binding glycoproteins in the subcommissural and the pineal organ of the sheep (Ovis aries)

Summary Glycoproteins rich in mannosyl or glucosyl residues were analyzed in the subcommissural organ (SCO) and the pineal organ of the sheep (Ovis aries). By use of concanavalin A labelled with fluorescein isothiocyanate, fluorescent material was found both in ependymal and hypendymal cells of the SCO. In the pineal organ, either isolated or grouped parenchymal cells showed a marked fluorescence. These cells may correspond to ependymal elements also called interstitial cells or supporting cells. In addition, scarce slender, fluorescent processes were observed in the pineal parenchyma. The techniques of electrophoresis and electrotransfer on nitrocellulose paper have been applied to analyze the glycopeptide content of the SCO and the pineal organ in comparison to cerebellar and cerebral fractions solubilized by use of Triton X 100. Approximately 30 different concanavalin A-reactive glycopeptides were revealed in each fraction. In the SCO extract four glycopeptides (30, 54, 72, 100 kd) might correspond to subunits of the glycoprotein(s) characteristically stored in the ependymal cells of the SCO. In addition, two glycopeptides (32/33, 115 kd) are specific to the pineal organ extract. The possible similarity of the concanavalin A-reactive material in both organs is discussed and a putative secretory activity of the pineal ependymal cells is postulated.     

Influence of very low doses of ionizing radiation on Synechococcus lividus metabolism during the initial growth phase

Previous results from this laboratory have shown that very low chronic doses of gamma radiation can stimulate proliferation of the Cyanobacterium Synechococcus lividus. This modification of cell proliferation occurred during the first doubling. In this paper, we have compared the metabolism of cells cultivated in a normal environment or under chronic irradiation. Incubation of the cells in a new medium induced a high superoxide dismutase (EC 1.15.1.1, SOD) activity at the 18th hour and a degradation of phycocyanin, thus demonstrating that cells were submitted to a photooxidative stress. This increase in superoxide dismutase activity was followed by concomittant peaks of glutathione reductase (EC 1.6.4.2, GR) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49, G6P-DH) at the 24th hour. Irradiated cultures at a dose of 53.5 mGray/year show an earlier and higher peak of SOD, GR, and G6P-DH. In a second stage, cultures showed an earlier onset of photosynthesis under irradiation, as evidenced by an increase in pigment content and an enhancement of glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13, GAP-DH). These results show that the radiostimulation is related to the activation of enzymes protecting against peroxides that were induced under oxidative circumstances and to the activation of a glucose catabolism via the oxidative pentose phosphate pathway.Abbreviations mGy milli-Gray - SOD superoxide dismutase - G6P-DH glucose-6-phosphate dehydrogenase - GAP-DH glycer-aldehyde-3-phosphate dehydrogenase - GSSG oxidized glutathione     

Larvae of Euphausia superba in the Scotia Sea and Bransfield Strait in March 1984 — Development and abundance compared with 1981 larvae

Summary Larvae of Euphausia superba in the Atlantic sector of the Antarctic in March 1984 averaged 580 per 1000 m³ of water. This is 100 times less than we observed in March 1981, but more than the average of 250 larvae per 1000 m³ found in January–February 1981. There was one 1984 high-abundance sample, accounting for 85% of all larvae caught, from the eastern area of confluence of Drake Passage and Weddell Sea waters. Abundances in 1984 near the South Shetland Islands were commonly 5 to 10 larvae per 1000 m³, and younger by 2 to 4 developmental stages than in March 1981. Body lengths of given stages were generally less in 1984 than in 1981. Advanced furcilia stages, particularly, in the 1984 samples tended to be smaller than the same stages in March 1981, indicating relatively poor growth during February 1984. However, the 1984 younger larvae (calyptopes and the developmental forms of furcilia stages 1 and 2) indicated that, in 1984, recent (March) growth had been good — probably better than in February. Dierct observation of the development of calyptopis stage 3 to furcilia stage yielded a development time of 7.7 days, which compares favorably to the 8-day period estimated from field samples. Reduced food availability did not affect the development rate nor give rise to a clearly higher incidence of indirect pathways of development. It is postulated that recruitment was about of month later in 1984 than in 1981 in most of the area studied and was probably going to be less successful.     

Effect of thyrotropin on glycosaminoglycans synthesized by primocultured thyroid cells

The synthesis of glycosaminoglycans (GAGs) was investigated in porcine thyroid cells under the influence or not of thyrotropin. After labelling with [³H] glucosamine and [³⁵S] $\text{SO}{}_4{}^{\mathrm{2?}}$, enriched GAG-fractions prepared from culture media, cells, and eventually substrate adhering materials, were analyzed by cellulose acetate electrophoresis combined with specific degradations. They comprised heparan sulfate and hyaluronic acid together with an unknown sulfated component labile to endo-β-galactosidase. Whereas global labellings of newly made GAGs were not significantly modified by thyrotropin, we reproducibly observed with the hormone a substantial increase in the proportion of hyaluronic acid [³H] label and, when cells organized into follicles, of the proportion of cell-associated [³H] GAGs. This system thus offers an interesting model to study how the responsiveness to an hormone and the reorganization that follows might implicate specific glycoconjugates.     

Isolation,purification and chemical composition of maize root cap slime

Summary The total root exudate isolated axenically from roots is shown to constitute an extremely heterogenous population of particulate and soluble material. Differences in protein and total sugars contents, and neutral sugar composition throughout stages of total root exudate purification are reported. The importance of controlled collection and purification conditions to ensure valid analysis and composition of purified maize root cap slime are discussed.     

Une triple translocation chez le Triton Pleurodeles waltlii

A cytogenetic study has lead us to a stock of fertile heterozygotes for a triple translocation. The chromosomal rearrangement has first been detected in a female resulting from a cross between a normal female and a male submitted to X ray-irradiation. The aberration consists of rearrangements between a chromosome 3, a chromosome 6 and a chromosome 7. Abnormal chromosomes have the following constitution: 7q?: the terminal portion of the long arm is lost and replaced by the end of the short arm of the chromosome 3. 6 q+: the terminal portion of the long arm is lost and replaced by the end of the long arm of the chromosome 7. 3p+: the terminal portion of the short arm is lost and replaced by the end of the long arm of the chromosome 6. On the analogy of the human chromosome standardization, the formula of heterozygotes is 24, t (3p+, 6q+, 7q?). The first meiotic division shows both in the female and in the male 9 bivalents and one hexavalent. The formulae of the gametes are the same in both sexes. When a heterozygote is bred with a normal individual the offspring is composed of phenotypically normal or abnormal animals, depending on their karyotypes. The unbalanced karyotypes are lethal or semilethal. The importance of the malformations depends on the temperature of the water where the animals grow. The study of the meiotic slides brings a cytological confirmation of the results obtained from the study of the phenotypes and karyotypes which appear in the offspring.