Biosynthesis of ecdysteroids by prothoracic glands in Pieris brassicae (Lepidoptera insect). Conversion in vitro of radiolabelled precursor of 3-dehydroecdysone]

Ecdysteroids secreted by prothoracic glands of Pieris brassicae were measured by enzyme immunoassay, after HPLC separation. Both ecdysone and 3-dehydroecdysone, as a major product, are produced. Two radiolabelled putative precursors were converted by Pieris glands in vitro: [3H] ketodiol was converted into ecdysone at a low rate; [3H]3-oxoketodiol was efficiently converted, mainly into 3-dehydroecdysone. These data make 3-oxoketodiol a good candidate for an intermediate in ecdysteroid biosynthetic pathway.     

Social behavior adaptations of gibbon (Hylobates lar) in a controlled environment

A population of six adolescent—adult gibbons (three males and three females) were observed in a controlled environment in order to assess any social behavior adaptations related to forced aggregation and to a physical environment which differed from the native habitat in that there were no predators, no food scarcity and the geographic range was limited to 1.5 acres. Data on location, size and composition of naturally formed social groupings revealed that certain gibbons avoided social contact with certain others. This observation is discussed in relation toChance's (1967) concept of “attention structure.” It is viewed as representative of a dominance hierarchy serving gibbons as a social behavior adaptation when forced to aggregate.     

CpFe-induced hexafunctionalization of hexamethylbenzene in [FeCp(η-C6Me6][PF6] using dendronized benzyl bromide derivatives at room temperature for the direct synthesis of metallodendrimers

Reaction of [FeCp(η⁶-C₆Me₆][PF₆] with KOH and benzylbromides parasubstituted with a functional dendron at room temperature selectively gives the hexasubstitution without decomplexation providing functional dendrimers, that were characterized by their molecular peaks in MALDI-TOF spectroscopy whereas, this chemistry was previously carried out at 60 °C which led to partial decomplexation and less selective reactions.     

Factors Affecting Elevated Arsenic and Methyl Mercury Concentrations in Small Shield Lakes Surrounding Gold Mines near the Yellowknife,NT, (Canada) Region

Gold mines in the Yellowknife, NT, region—in particular, the Giant Mine—operated from 1949–99, releasing 237,000 tonnes of waste arsenic trioxide (As₂O₃) dust, among other compounds, from gold ore extraction and roasting processes. For the first time, we show the geospatial distribution of roaster-derived emissions of several chemical species beyond the mine property on otherwise undisturbed taiga shield lakes within a 25 km radius of the mine, 11 years after its closing. Additionally, we demonstrate that underlying bedrock is not a significant source for the elevated concentrations in overlying surface waters. Aquatic arsenic (As) concentrations are well above guidelines for drinking water (10 μg/L) and protection for aquatic life (5 μg/L), ranging up to 136 μg/L in lakes within 4 km from the mine, to 2.0 μg/L in lakes 24 km away. High conversion ratios of methyl mercury were shown in lakes near the roaster stack as well, with MeHg concentrations reaching 44% of total mercury. The risk of elevated exposures by these metals is significant, as many lakes used for recreation and fishing near the City of Yellowknife are within this radius of elevated As and methyl Hg concentrations.     

Toxic Effect of Cysteine Against Salmonella typhimurium

Cysteine was shown to be toxic to Salmonella typhimurium. The mechanism of this toxicity may be due, at least in part, to cysteine's ability to cause deoxyribonucleic acid strand scissions.     

Photochemotherapy using pyridopsoralens

Aiming to decrease the acute side effects and genotoxic hazards of PUVA, pyrido (3,4-C) psoralen (PP) and 7-methyl pyrido (3,4-C) psoralen (MPP) were synthesized and studied. Their UVA maximum absorption lies at 325 and 330 nm, respectively. Their photostability is comparable to that of 8-MOP. They complex to DNA in the dark, and, in the presence of UVA, produce only monoadditions to DNA, as shown by fluorescence and DNA denaturation-renaturation studies. In diploid eukaryotic yeast they are more effective than 8-MOP for the induction of lethal effects and mitochondrial damage. Their mutagenic activity per unit dose of UVA is in the same range as that of 8-MOP. However, per viable cell they are clearly less mutagenic than 8-MOP. This difference is also observed for recombinogenic activity. No oxygen effect is observed. In mammalian cells the following ranges of effectiveness are found: inhibition of DNA synthesis in human fibroblasts: MPP greater than PP greater than 8-MOP; mutagenic activity in V79 Chinese hamster cells: MPP greater than PP greater than 8-MOP; cell transforming ability in C3H embryonic mouse cells: MPP greater than 8-MOP greater than PP as a function of UVA dose, and: 8-MOP greater than MPP greater than PP as a function of survival; induction of sister chromatic exchanges (SCE) per unit dose: MPP greater than PP greater than 8-MOP in the linear part of the induction curve, and : 8-MOP greater than PP greater than MPP at the maximum level of SCE obtained.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence du d?bit d'eau de mer dans un dispositif de culture ? fibres creuses dialysantes sur la croissance phytoplanctonique et 1'extraction des nitrates du milieu

It is demonstrated that the productive capacity of mass dialysisculture of phytoplankton is intimately related to the rate offlow of nutrient medium along the membrane. Comparison of culturesof Phaeodactylum tricornutum, subject to different medium flowrates (92 versus 250 ml.min^–1) during a 17-day growthperiod, reveals increased productivity (in terms of cell numbers,chlorophyll a, dry weight, cell nitrogen, cell carbon, ATP)at the higher flow rate. Differences are most pronounced inthe latter stages of growth (i.e., linear and stationary) attainingratios between 2 and 3 for cell nitrogen, cell carbon and ATP.Lower C/N ratios for the greater yielding culture translatesas enhanced osmotic diffusion as well as cellular assimilationof nitrates. The positive effects of increasing medium flowrate on phytoplankton growth result from improved dialyzer performancewith respect to low molecular weight solutes. This is evidencedin the proportionately greater values obtained for mass transferof nitrate-nitrogen. Accordingly, measures of nitrate clearanceindicate a progression from 29 to 85 ml.min^–1 in responseto augmenting sea water flow from 32 to 292 ml.min ^–1.The culture apparatus recently developed consists of a separatedialysis unit (a hollow-fiber cartridge used in hemodialysis)coupled to a temperature-controlled growth chamber. Culturesreceive a continuous flow of natural sea water and are grownin the batch dialysis mode. The main advantages of this methodrelate to its potential for large-scale, axenic algal culturebased on the abundant source of cheap nutrients that constitutesnatural sea water.     

Ecdysones and imaginal disc development during the last larval instar of Pieris brassicae

Ecdysone haemolymph levels and in vivo development of imaginal wing discs have been studied during the last larval instar of Pieris brassicae.During this period, β-ecdysone variations show two successive peaks, the first one related to the induction of wandering stage, and the second (main) one to pupal cuticle synthesis. The observed situation is very similar to that of Manduca sexta. Imaginal wing disc growth is composed of several genetically programmed steps that need the presence of ecdysone, but do not appear very closely linked to circulating hormone levels. It seems that ecdysone haemolymph peaks should be considered as periods where ecdysone levels are above a threshold value.