Croissance et synthese des proteines de suspensions cellulaires de Tabac sensibles à la kinétine

Culture conditions, allowing the unlimited growth and maintenance in shaken suspensions of a kinetin dependent strain of tobacco pith cells, were determined. Cell clusters from 1 to 25 cells were selected from the cultures to study the cell multiplication after addition of specific growth factors to the basal medium. Cell division was found to be strictly dependent upon the presence in the medium of both kinetin and auxin. In complete medium the generation period was 45 to 49 hours. Kinetics of the total protein synthesis in the cell suspensions have been measured either by estimation of protein nitrogen or by ³⁵S incorporation into the proteins. After 3 days of culture, growth was exponential, as expressed by cell number or protein synthesis, which varied proportionally. Evidence was also found that the initial incorporation rate of radioactivity into the proteins was more rapid than expected from the increment of the protein net weight. It seems therefore reasonable to assume that a significant amount of protein turn over does exist during the initial period of growth. This phenomenon was observed even when no cell division occurred. Kinetin significantly activated protein synthesis, whether or not auxin was present in the medium.     

Action de la kinétine sur la croissance et la teneur en chlorophylles des racines

Lens roots form chlorophylls in well-developed chloroplasts when they are cultivated in continuous light. Chlorophyll accumulation was increased when kinetin (10^?4M) was added for a short time (24 h) of treatment. For a long time (72 h), the increase of chlorophyll content was reduced when roots were cultivated in light and with kinetin. When the roots were transferred from light to dark, chlorophyll content was decreased. This reduction was inhibited when roots were treated with kintin. From these present result it was supposed that kinetin acts on the catabolism and the anabolism of chlorophyll. The necessity of kinetin for chloroplast from amyloplast maturation and differentiation was discussed.     

Influence des variations expérimentales de la calcémie sur la morphologie fine des cellules C du rat et du poulet

Résumé Les expériences d'hypercalcémie aigües et chroniques provoquent chez le rat des modifications spectaculaires des cellules C. Ces résultats sont en accord avec les données physiologiques sur la sécrétion de calcitonine chez le mammifère. Chez le poulet, par contre, les mêmes expériences ne provoquent pas de modifications indiscutables des Corps ultimobranchiaux (C.U.B.). Seule, l'injection intraveineuse de calcium provoque une dégranulation d'ailleurs partielle et assez peu accusée, des cellules C. L'inertie réactionnelle des C.U.B., que nous constatons morphologiquement, ressort également des données contradictoires sur le rôle physiologique de la calcitonine chez l'oiseau.

---

Influence of experimental modifications of calcemia on the fine structure of the C-cells in rat and in chicken

Summary Acute and chronic hypercalcemia in rats induce spectacular modifications of the C cells. These results are in agreement with the physiological data on calcitonin secretion in mammals. The same experiments in chickens, however fail to provide a net modification of the ultimobranchial body. Only an intravenous injection of calcium induces degranulation of the C cells, and even then, this is partial and hardly evident. The lack of the ultimobranchial body response as observed in our morphological study may be compared with the conflicting physiological data on the role of calcitonin in birds.

     

Synthèses ďacides nucléiques et de protéines au cours de ľinitiation de bourgeons adventifs sur des explantats de Cichorium intybus cultivés in vitro

Synthesis of nucleic acids and proteins during initiation of vegetative buds from explants of Cichorium intybus cultivated in vitro .
Explants of 6 mm diameter and 2 mm thickness from roots of Cichorium intybus L. (var. WitIoof cv. "Zoom"), grown in vitro in the presence of kinetin (l0_–6 M ), produced only buds. By comparing the histological events and the biochemical modifications which occurred during the neoformation of buds, it is possible to distinguish two distinct phases. The first phase starts immediately after the excision of the explants and continues for 30 h, when the mitotic index is at its highest. This corresponds to a phase of cellular activation, which is characterized by early synthesis of RNA, permitting the synthesis of proteins necessary for duplication of DNA and cell divisions. The second period starts after 30 h and ends after approximately 72 h of culture, at which time the first bud meristematic nodules were detected. This is a preparatory phase for organogenesis and above all related to synthesis of RNA and proteins.     

Influence de l'intensité et de la longueur d'onde de la lumière sur le rendement des radicaux libres dans les semences de tomate et de carotte

Influence of light intensity and wavelength on the yield of free radicals in seeds of tomato and carrot.
Seeds of tomato ( Lycopersicum esculentum L. cv. Gribovsky-1180) and carrot ( Daucus carota L. cv. Santanet) were irradiated by continuous light of different wavelengths (white, blue, green, red, far-red and He-Ne laser) and different power density. Free radical output was measured using Electron Spin Resonance spectra (ESR). The dependence of the content of free radicals (FR) on the light power density was established. The yield of FR in the seeds irradiated with monochromatic light of the same power density was inversely proportional to the wavelength. The ESR spectra showed maximum absolute number of FR for white light. Successive irradiations gave cumulative effects on the output of free radicals in both directions: increase by the action of white light and decrease by the action of red and far-red light. The contact of irradiated seeds with steam decreased the amount of FR.     

Influence ďune alimentation continue avec une solution glucosée sur ľévolution des glucides et des protéines dans les divers organes de la rose coupée (Rosa hybrida cv. Carina)

Influence of continuous supply with a solution of glucose on the changes in the content of soluble sugars and proteins in various organs of the cut rose (Rosa hybrida cv. Carina). Exogenous glucose continuously supplied to the cut rose is immediately converted into saccharose in the stem tissues. This saccharose migrates to the flower, where it is immediately hyd-rolysed, and to the leaves where its hydrolysis occurs more slowly. The reducing sugars resulting from the hydrolysis of saccharose in the flower and, therefore, possibly from the hydrolysis of saccharose in leaves, induce a large accumulation of hexoses (glucose and fructose) in the flower. The protein content does not depend on the level of reducing sugars in the flower.     

Étude de l’effet des thiosemicarbazones sur Toxoplasma gondii

Toxoplasmosis is a neglected disease, with an estimated occurrence of one-third of the population worldwide. Research in medicinal chemistry has for some years been pursuing the development of new drugs against toxoplasmosis, because current treatments cause serious side effects in the patient. The use of thiosemicarbazones as an alternative option for the treatment of various diseases has been published in recent years, due to their, among others, anticancer, antimalarial, antitrypanosomal, antibacterial, and antitoxoplasmosis activities, the latter being the subject of this study, which is based upon biological analyses and tests of the response of Toxoplasma gondii in the presence of thiosemicarbazones.     

Influence relative de la BAP et de l'IBA sur la néoformation de bourgeons et de racines sur les plantules du Biota orientalis (Cupressacées)

Relative influence of BAP and IBA on the induction of adventitious buds and roots on plantelts of Biota orientalis (Cupressaceae)
Both cytokinin (BAP) and auxin (IBA) have an influence upon the intensity of adventitious bud induction in vitro on hypocotyls of Biota orientalis .
Increase in either the concentration or the length of contact with cytokinin enhances the mean number of neoformed buds per explant, while that of auxin results in an increase of the mean number of reactive explants as well as in the nature of neoformations. Auxin contributes to a restoration of the induction when the length of contact with cytokinin is too short. However, this synergism is only observed when the contract with IBA is simultaneous or follows that with contract with BAP.
Rhizogenesis is also influenced by the auxin-cytokinin balance. An increase in the duration of contact with IBA is always followed by an increased in the mean number of explants forming roots. This organogenesis may be partially or completely inhibited if the duration of contact with cytokinin – before, simultaneously or after that with auxin- exceeds two weeks.