Showing papers by "University of Bordeaux published in 1975"

Sums involving the values at negative integers of L-functions of quadratic characters

Abstract: For each integer r > 1 we will define an arithmetic function H(r, N) which for r = 1 is the class number of (not necessarily primitive) quadratic forms of discriminant N and for r > 1 is essentially the value of ~K(r) where K = ~ ( ] / ~ ) . For r > 2 the function ~N>_0 H(r, N)e 2~i~ is a modular form of weight r + 1/2 on Fo(4 ). This implies numerous identities involving H(r, N). The analogous formulas for r = 1 (which do not follow from the methods of this paper) are classical "class number relations" of Kronecker, Hurwitz and others, as well as certain generalizations coming from the Selberg-Eichler trace formula and from recent work of Hirzebruch-Zagier. One of the tools used is of independent interest: given two modular f o r m s f a n d 9, there are certain bilinear expressions in the derivatives o f f and 9 which are again modular forms.

pH dependence of singlet oxygen production in aqueous solutions using thiazine dyes as photosensitizers.

Abstract: — The production of singlet oxygen by thiazine dye photosensitization, as measured by the rate of photooxidation of tryptophan, was found to be very sensitive to changes of pH in the range 5–9. For methylene blue in aerated solutions, the production of 1O2* is approximately five times more efficient in basic than in acidic medium. This was shown to be related to the pK's of the triplet dyes, by evaluating the yields of 1O2* from the lifetimes and the quenching rate constants for the two ionic species of sensitizer triplets measured by laser flash photolysis. Changes in the quenching rate constants of the thiazine triplet states can be correlated with the triplet energies.

Activity of phasic neurosecretory cells during haemorrhage.

Abstract: APPROXIMATELY 25% of the neurones projecting to the neurohypophysis from the paraventricular (PV) and supraoptic (SO) nuclei of the hypothalamus fire phasically and such a pattern is seldom seen in other hypothalamic cells1. Phasic neurones respond to osmotic stimuli2 but are rarely activated by suckling1,3. It is tempting therefore, to associate these cells with the secretion of vasopressin rather than oxytocin. The functional relationship of their phasic pattern to hormone release, however, remains obscure. We have studied phasic PV neurones during haemorrhage, which releases vasopressin, sometimes with small amounts of oxytocin4. Haemorrhage evoked changes in phasic units over a period long enough for a detailed analysis of their behaviour. Our results show the importance of pattern modulation in phasic neurones and suggest that the mechanism for vasopressin release differs from that described for oxytocin release during suckling1,3.

Concentration of Dipropylacetate in Plasma

Abstract: SUMMARY Dipropylacetate is absorbed rapidly and attains a maximum concentrati n in serum 1 to 3 hr after ingestion. Since its half-life is on the order of 8 to 10 hr, it must be prescribed three times a day, every 8 hr. It reaches a stable concentration in blood within 48 hr after treatment is begun (by contrast with diphenyl-hydantoin and phenobarbital) and might therefore be useful when seizures must be controlled quickly. The serum concentration can be altered by some other anticonvulsant drugs, butThese interactions should be studied in more detail. The serum concentration varies considerably in the course of a day and from one day to the next in the same subject, which makes it difficult to adjust the blood level. Depamide is rapidly transformed in vivo to dipropylacetate. RESUME Le dipropylacetate de sodium est rapidement absorbe et atteint sa concentration serique maximum une a trois heures apres son ingestion. Puisque sa demi-vie est de l'ordre de 8 a 10 heures, il doit etre present 3 fois par jour, toutes les 8 heures. 11 atteint une concentration sanguine stable en moins de 48 heures apres de deiwt du traitement (contrairement a la diphenylhydantoi'ne et au phenobarbital) et peut ainsi Stre utile quand des crises doivent etre controlees rapidement. La concentration serique peut etre modifiee par quelques autres antiepileptiques, mais ces interactions restent a preciser. La concentration serique varie con-siderablement dans le cours de la journee et d'un jour a 1'autre chez le mime sujet, ce qui rend difficile l'ajustement du taux sanguin. L'amide de l'acide dipropylacetique, Depamide, est rapidement transform^ in vivo en acide dipropylacetique. RESUMEN El dipropilacetato se absorbe rapidamente alcanzando la maxima concentracidn serica entre 1 y 3 horas despues de la ingestion. Su administration debe realizarse cada 8 horas (3 veces diarias) puesto que su vida media es de 8 a 10 horas aproximSdamente. Alcanza una concentracidn estable en sangre dentro de las 48 horas de iniciarse el tratamiento (en contraste con la difenilhidantoina y fenobarbital) por lo que puede ser utilizado cuando se necesite un control rapido de los ataques. Las concen-traciones sericas pueden ser modificadas por otras drogas anticonvulsivas pero, de todos modos, estas interacciones deben estudiarse con mas detalle. Los niveles en suero varfan consid-erablemente a lo largo del dla y de dla a dla en un mismo individuo por lo que resulta dificil ajustar los citados niveles. Depamida se trans-forma rapidamente in vivo en dipropilacetato. ZUSAMMENFASSUNG Dipropylazetat wird rasch resorbiert und erreicht eine maximale Serumkonzentration 1–3 Stunden nach Einnahme. Da seine Halbwerts-zeit etwa 8–10 Stunden betragt, muss es 3 Mai taglich alle 8 Stunden verschrieben werden. Es erreicht im Blut eine stabile Konzentration innerhalb 48 Stunden nach Therapiebeginn (im Gegensatz zu Diphenylhydantoin und Pheno-barbital) und ist deshalb zu empfehlen, wenn Anfalle rasch unter Kontrolle gebracht werden miissen. Die Serumkonzentration kann durch einige andere Antikonvulsiva beeinflusst werden; diese Interaktionen sollten genauer untersucht werden. Die Serumkonzentration schwankt betrachtlich im Verlaufe eines Tages und von Tag zu Tag intraindividuell. Das macht es schwierig, den Blutspiegel festzulegen. Depamide wird in vivo rasch in Dipropylazetat uberfuhrt.

Observation of click-evoked compound VIII nerve responses before, during, and over seven months after kanamycin treatment in the guinea pig.

Abstract: Compound VIII nerve action potential responses to clicks and filtered-clicks were recorded regularly over a period of 7 months following Kanamycin treatment (8 days, 400 mg/kg), in 3 awake guinea pigs each with an implanted electrode on the round window (left ear). From the end of the treatment the responses to the click became dissociated in various degrees within three major phases: (1) a rapid phase (8 to 10 days) where the responses were dramatically altered, (2) a recovery phase which lasted about 2 months, (3) a slow phase over the subsequent 5 months where the responses to the click decreased slowly but gradually while the N 1 component, as well as the responses to the 8 000 Hz filtered-click (which became recruiting at the end of the treatment), disappeared progressively. Responses to the low frequency filtered-clicks were less affected. Cochlear cyto-grams showed almost complete degeneration of the inner and outer hair cells of the first turn only.

pH dependence of singlet oxygen production in aqueous solutions using toluidine blue as a photosensitizer.

Abstract: In a recent article (Bonneau et al., 1975), we reported the variation of photosensitized '02 production via methylene blue and thionine as a function of pH and showed this variation to be directly related to: (1) the energy difference between the triplet dye (donor) and singlet oxygen (acceptor) and (2) lifetimes of the triplet dye. At that time we also predicted that toluidine blue, a thiazine dye which has found important applications in photobiology as an effective electron acceptor (Hasegawa et al., 1969; Mathis, 1972) should also show a wide variation of photosensitized '0, production as a function of pH. If such a variation of photosensitized '02 production as a function of pH occurs for toluidine blue, we deemed it necessary to examine its extent and range of greatest sensitivity. As pointed out for methylene blue, a slight change of pH in the near neutral zone can significantly change the '0, production. Thus, depending on the exact pH of the solution and whether or not the solution is buffered, one could conceivably classify toluidine blue as a good or a poor sensitizer. One of the toluidine blue acid-base equilibria can be represented as in the triplet state as being equal to 7.6 f 0.5, using the flash photolysis technique. Using a laser flash photolysis technique previously described (Bonneau et al., 1975) we have measured, in both slightly acidic and basic media, the quenching rate constants by oxygen for toluidine blue triplet states. For non-buffered aqueous solutions of toluidine blue, concentration being 3 x M , the quenching rate constants for the triplet states are 2.9 x 10' mol-'s-' at pH 3 for the 3BH:' species and 3.3 x lo9 mol-' s' at pH 8 for the 'BH' species. Under the same experimental conditions the lifetimes of the triplet species in the absence of oxygen were measured as 5ps for 3BHif (PH 3) and 60ps for 3BH' (PH 8). From the rate constants it is possible to evaluate the quantum yield of '0, production, assuming, in analogy with other thiazine dyes studied, a simple energy transfer process as shown:

Infection of brassica leaf protoplasts by turnip yellow mosaic virus

Abstract: Summary. Conditions optimal for the infection of Brassica leaf protoplasts by turnip yellow mosaic virus (TYMV) were found to be: pH 5.4-5.8 with citrate buffer; concentration of poly-L-ornithine, Izg/ml; concentration of TYMV, 0.2-1.0 lzg/ml. More than 90% of Brassica rapa and B. sinensis protoplasts were infected under these conditions. TYMV replication in Brassica protoplasts was followed by quantitating the virus extracted from protoplasts and separated by sucrose density gradient centrifugation. Brassica protoplasts produced I to 2 × 106 TYMV particles per cell within 48 hrs. Infection by TYMV induced the formation of polyplasts (aggregates of chloroplasts) in Brassica protoplasts. Polyplast formation paralleled the appearance of TYMV-specific immunofluorescence and could thus be used conveniently to determine the number of infected protoplasts. TYMV replication in Brassica protoplasts was resistant to actinomycin D and chloramphenicol, but was completely inhibited by cycloheximide.

Response of Earthworm Leukocytes to Concanavalin a and Transplantation Antigens

Abstract: There are several reasons to believe that rejection of both allogenic and xenogenic tissues by earthworms is due to an active immune response: a second graft from a same donor to a same receptor is more actively rejected (1); graft immunity can be transfered by coelomic cells from a sensitized animal to a non sensitized one (2). Coelomic cells, which are the free cells of the coelomic cavity, mainly consist in leukocyte-like cells. The leukocytes undoubtly play a prominent role in graft rejection in earthworms: it seems that they recognize the immunogenic stimulus and then proliferate and differentiate into cells that attack the grafted tissues (3). In vertebrates, specific recognition is achieved by a special group of leukocytes, the lymphocytes (4), that generally proliferate after antigenic stimulation. The leukocytes can also exibit an increase of DNA synthesis after a wound. But, in vertebrates, stimulated cells involved in inflammation are different from lymphocytes. In order to check whether graft reaction in earthworms was different from inflammatory process, we have compared the leukocyte stimulation induced by wound with that occuring after graft. The quantitative aspects of the stimulation have been investigated as well as the nature of the stimulated cells.

Mechanism of photoreduction of thiazine dyes by EDTA studied by flash photolysis III. Consequences of a newly found pKT of thionine on the mechanism in basic solutions.

Abstract: — Evidence for an acid-base equilibrium between the neutral and monocationic forms of the triplet state of thionine, 3T and 3TH+ (pKT# 8–9) has been found. This equilibrium, which has no counterpart in the methylene blue system can explain the different behaviours of these two similar dyes concerning their photoreduction by ethylene diamine tetracetic acid (EDTA) in basic solutions. With reasonable assumptions about the reactivity of the various species present in solution, it is now possible to calculate over the whole pH range the quantum yield of semireduced dye formation φs, which, according to the previously proposed mechanism, must be proportional to the overall photoreduction quantum yield φR. The very good fit between the calculated curve φs =f(pH) and the experimental one φR =f(pH) for both dyes strongly supports the proposed mechanism.