Molecular structure of peptaibol antibiotics: solution conformation and crystal structure of the octapeptide corresponding to the 2-9 sequence of emerimicins III and IV

The infrared absorption and 1H nuclear magnetic resonance analyses of chloroform solutions of the terminally-blocked segment corresponding to the 2-9 sequence of emerimicins III and IV, -(Aib)3-L-Val-Gly-L-Leu-(Aib)2-, are consistent with the presence of a 3(10)-helical structure of high thermal stability. The crystal structure of the octapeptide, obtained by X-ray diffraction indicates the formation of a right-handed 3(10)-helix, stabilized by six consecutive intramolecular N-H....O:C H-bonds, slightly distorted at the level of the L-Leu residue.     

Callus formation and induction of a cell suspension culture from Acacia senegal

Cell proliferation has been induced from the cambial zone of a branch of Acacia senegal, kept on the basal Knop and Ball medium in the presence of auxin. Transferred on the more complete nutrient medium of Schenk and Hildebrandt, the colonies gave rise to several cell lines. One of the friable lines, consisting of aggregates of parenchymatous cells, gave a cell suspension culture in an agitated liquid medium which is maintained as a strain of illimited growth. The heterogeneous suspension did not undergo noticeable changes after eight transfers. Aggregates collected on a 1000-m nylon seive were able to grow on a solid medium and gave back a friable callus similar to the initial colonies.     

HIBERNATION CHEZ TROIS ESPÈCES DE MÉTOPIINES: HYMENOPTERA,ICHNEUMONIDAE

Résumé Les conditions de l'hibernation sont étudiées chez les trois espèces de Métopiines Chorinaeus funebris Gravenhorst, Triclistus podagricus Gravenhorst et Triclistus pygmaeus Cresson. Ces espèces hibernent à des stades de développement compris entre l'éonymphe et l'adulte non émergé (Tableau I). La durée de l'incubation complémentaire après réactivation par le froid à 2^o varie entre 10 et 30 jours en moyenne (Tableaux II, IV et V). Chez T. podagricus et T. pygmaeus, on a observé également des émergences d'adultes avant l'hiver (Tableau III). I1 semble que T. podagricus ne parvienne au stade d'imago hibernant qu'après une baisse de la température d'élevage. Aucune souche dépourvue de diapause n'a pu être créée, mais pour les trois espèces, deux générations annuelles seraient possibles sous conditions contrôlées. Enfin, l'utilisation éventuelle de T. pygmaeus pour une lutte biologique contre Zeiraphera diniana Guénée est évoquée.

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Summary The conditions of hibernation have been investigated in the three metopiine species Chorinaeus funebris, Triclistus podagricus and Triclistus pygmaeus, all entomophagous on Zeiraphera diniana Guénée (Lepidoptera, Tortricidae) in the Engadine Valley (Switzerland). The hibernating stages are eonymph, pronymph or unemerged adult inside the host pupae (Table I). The length of the complementary incubation after reactivation at 2^o varies between 10–30 days (Tables II, IV and V). A small number of T. podagricus and of T. pygmaeus regularly appear as adults before winter, in rearings of both laboratory and field populations (Table III). It seems that T. podagricus larvae need a reduction in the initial rearing temperature before full development is achieved and the hibernating stage is reached (imago). No strain without diapause could be obtained for any of the three species, but the rearing of two annual generations under controlled conditions is possible in the laboratory. The eventual use of T. pygmaeus as a control agent against Z. diniana is discussed.

     

New data on the toxic and radioprotective effect of cysteine onEscherichia coli 15 T- cells

Summary Exponential phase cultures ofE. coli 15 T^- cells growing on glucosemineral medium were supplemented with 2 mM l-cysteine-HCl. The optical density, acid soluble SH (AS-SH) as well as the DNA, RNA, and protein synthesis of the cultures were examined during this treatment and after return to normal growth conditions. Similarly, the survival of cells irradiated by a standard X-ray dose in cysteine-free buffer was measured.The development of radioresistance during the cysteine treatment as well as the loss of this acquired radioresistance after return to normal growth conditions could be divided into two phases: a) an instantaneous and b) a slow change of radioresistance. Phase a seems to be related to the changes occurring in the AS-SH content of the bacteria, while phase b is apparently dependent on the alterations in the synthesis of macromolecules.This work was partly presented at the 6th Annual Meeting of the European Society for Radiation Biology, Interlaken 1968.     

Antiestrogenic and antitumor properties of the new triphenylethylene derivative toremifene in the rat

The effects of toremifene, a new triphenylethylene derivative, on the uterus and DMBA-induced mammary tumors in rats were compared to tamoxifen. The ability of toremifene to compete with [3H]estradiol for cytoplasmic estrogen receptor from rat uterus was similar to tamoxifen, the IC50 being 26 and 23 microM respectively. In immature intact rats the two compounds, administered orally for three consecutive days, had similar intrinsic partial estrogenic efficacy, at 50 mg/kg, about 40% of that of estradiol benzoate (EB). However, at doses less than or equal to 10 mg/kg, the estrogenic effect of toremifene was seen at doses about 40 times higher than that of tamoxifen. The two compounds, administered together with a standard dose of EB, expressed the same maximal antiestrogenic efficacy (about 65% inhibition) at 50 mg/kg. However, the minimal effective antiestrogenic dose of toremifene was about 10 times that of tamoxifen and the ratio between antiestrogenic/estrogenic properties was favourable to toremifene. The duration of the antiestrogenic (antiuterotrophic) effect of a single oral dose (10 mg/kg) of the two compounds proved similar: at least 4 days in intact rats and 3 days in ovariectomized rats. In DMBA-induced tumor bearing rats toremifene was administered p.o., 6 times/week for 4 weeks at 0.08, 0.4, 2, 10 and 50 mg/kg. It was effective at the doses of 2, 10 and 50 mg/kg, inducing 39, 35 and 46% tumor regressions. The activity of toremifene at the minimal effective dose of 2 mg/kg was then compared with that of tamoxifen given at the same dose level. The compounds had comparable activity (47 vs 44% tumor regressions).     

Reproductive performance of Coopworth ewes following oral doses of zearalenone before and after mating

The reproductive performance of Coopworth ewes after administration of zearalenone was determined in two trials. In Trial I, zearalenone was administered to groups of 33 ewes at rates of 0, 1.5, 3.0, 6.0, 12.0 and 24.0 mg/ewe/day for 10 days, starting on Day 7 of the oestrous cycle before mating. There was a linear decline (P less than 0.001) in ovulation rate with dose of zearalenone; also cycle length decreased and duration of oestrous increased with increasing dose levels. Reductions in the incidence of ovulation and in fertilization were seen only at doses of 12 and 24 mg. In Trial 2, groups of 50 ewes were given the same range of doses of zearalenone for 10 days, starting 5 days after mating to entire rams. There was no effect of zearalenone treatment after mating on pregnancy rate or embryonic loss. These results indicate that the effects of zearalenone, administered orally, on ewe reproduction, at the dose levels examined, were restricted to ewes exposed before mating. Intakes of zearalenone of 3 mg/ewe/day or more during this period would be reflected as depressed ovulation rates and lower lambing percentages.     

Index of new names of syntaxa published in 1992

The present work collects the new names of syntaxa (in the sense of the Code of Phytosociological Nomenclature,Barkman et al. 1986) above subassociation, rank found in the literature received by the Library of the Conservatoire et Jardin botaniques in Geneva. For the year 1992, 658 names have been listed. For each one of them, an appreciation about its validity is given relating to the Code of Phytosociological Nomenclature. Fifteen names are given in addition to the Indexes 1987, 1990 and 1991 (Theurillat & Moravec 1990, 1993, 1994).     

Effects of prolonged cycle ergometer exercise on maximal muscle power and oxygen uptake in humans

The mechanical power (W_tot, W·kg^–1) developed during ten revolutions of all-out periods of cycle ergometer exercise (4–9 s) was measured every 5–6 min in six subjects from rest or from a baseline of constant aerobic exercise [50%–80% of maximal oxygen uptake (VO_2max)] of 20–40 min duration. The oxygen uptake [VO₂ (W·kg^–1, 1 ml O₂ = 20.9 J)] and venous blood lactate concentration ([la]_b, mM) were also measured every 15 s and 2 min, respectively. During the first all-out period, W_tot decreased linearly with the intensity of the priming exercise (W_tot = 11.9–0.25·VO₂). After the first all-out period (i greater than 5–6 min), and if the exercise intensity was less than 60% VO_2max, W_tot, VO₂ and [la]_b remained constant until the end of the exercise. For exercise intensities greater than 60% VO_2max, VO₂ and [la]_b showed continuous upward drifts and W_tot continued decreasing. Under these conditions, the rate of decrease of W_tot was linearly related to the rate of increase of V [(d W_tot/dt) (W·kg^–1·s^–1) = 5.0·10^–5 –0.20·(d VO₂/dt) (W·kg^–1·s^–1)] and this was linearly related to the rate of increase of [la]_b [(d VO₂/dt) (W·kg^–1·s^–1) = 2.310^–4 + 5.910^–5·(d [la]_b/dt) (mM·s^–1)]. These findings would suggest that the decrease of W_tot during the first all-out period was due to the decay of phosphocreatine concentration in the exercising muscles occurring at the onset of exercise and the slow drifts of VO₂ (upwards) and of W_tot (downwards) during intense exercise at constant W_tot could be attributed to the continuous accumulation of lactate in the blood (and in the working muscles).     

Polymorphic tandem repeat region in interleukin-1α intron 6

Analysis of polymerase chain reaction amplified products from the sixth intron of the human interleukin-1 gene reveals a high polymorphism (polymorphism information content = 0.51) in a Caucasian population. Altogether, seven alleles have been defined ranging from 620 to 1220bp. This polymorphism is probably attributable to a variable number of 46-bp tandem repeats, each containing potential regulatory sequences.