The Selectivity of Milking of Dunaliella salina

The process of the simultaneous production and extraction of carotenoids, milking, of Dunaliella salina was studied. We would like to know the selectivity of this process. Could all the carotenoids produced be extracted? And would it be possible to vary the profile of the produced carotenoids and, consequently, influence the type of carotenoids extracted? By using three different D. salina strains and three different stress conditions, we varied the profiles of the carotenoids produced. Between Dunaliella bardawil and D. salina 19/18, no remarkable differences were seen in the extraction profiles, although D. salina 19/18 seemed to be better extractable. D. salina 19/25 was not “milkable” at all. The milking process could only be called selective for secondary carotenoids in case gentle mixing was used. In aerated flat-panel photobioreactors, extraction was much better, but selectiveness decreased and also chlorophyll and primary carotenoids were extracted. This was possibly related to cell damage due to shear stress

Stress-Induced Reinstatement of Drug Seeking: 20 Years of Progress

In human addicts, drug relapse and craving are often provoked by stress. Since 1995, this clinical scenario has been studied using a rat model of stress-induced reinstatement of drug seeking. Here, we first discuss the generality of stress-induced reinstatement to different drugs of abuse, different stressors, and different behavioral procedures. We also discuss neuropharmacological mechanisms, and brain areas and circuits controlling stress-induced reinstatement of drug seeking. We conclude by discussing results from translational human laboratory studies and clinical trials that were inspired by results from rat studies on stress-induced reinstatement. Our main conclusions are (1) The phenomenon of stress-induced reinstatement, first shown with an intermittent footshock stressor in rats trained to self-administer heroin, generalizes to other abused drugs, including cocaine, methamphetamine, nicotine, and alcohol, and is also observed in the conditioned place preference model in rats and mice. This phenomenon, however, is stressor specific and not all stressors induce reinstatement of drug seeking. (2) Neuropharmacological studies indicate the involvement of corticotropin-releasing factor (CRF), noradrenaline, dopamine, glutamate, kappa/dynorphin, and several other peptide and neurotransmitter systems in stress-induced reinstatement. Neuropharmacology and circuitry studies indicate the involvement of CRF and noradrenaline transmission in bed nucleus of stria terminalis and central amygdala, and dopamine, CRF, kappa/dynorphin, and glutamate transmission in other components of the mesocorticolimbic dopamine system (ventral tegmental area, medial prefrontal cortex, orbitofrontal cortex, and nucleus accumbens). (3) Translational human laboratory studies and a recent clinical trial study show the efficacy of alpha-2 adrenoceptor agonists in decreasing stress-induced drug craving and stress-induced initial heroin lapse

Cocaine Is Low on the Value Ladder of Rats: Possible Evidence for Resilience to Addiction

International audienceBACKGROUND:Assessing the relative value of cocaine and how it changes with chronic drug use represents a long-standing goal in addiction research. Surprisingly, recent experiments in rats--by far the most frequently used animal model in this field--suggest that the value of cocaine is lower than previously thought.METHODOLOGY/PRINCIPAL FINDINGS:Here we report a series of choice experiments that better define the relative position of cocaine on the value ladder of rats (i.e., preference rank-ordering of different rewards). Rats were allowed to choose either taking cocaine or drinking water sweetened with saccharin--a nondrug alternative that is not biologically essential. By systematically varying the cost and concentration of sweet water, we found that cocaine is low on the value ladder of the large majority of rats, near the lowest concentrations of sweet water. In addition, a retrospective analysis of all experiments over the past 5 years revealed that no matter how heavy was past cocaine use most rats readily give up cocaine use in favor of the nondrug alternative. Only a minority, fewer than 15% at the heaviest level of past cocaine use, continued to take cocaine, even when hungry and offered a natural sugar that could relieve their need of calories.CONCLUSIONS/SIGNIFICANCE:This pattern of results (cocaine abstinence in most rats; cocaine preference in few rats) maps well onto the epidemiology of human cocaine addiction and suggests that only a minority of rats would be vulnerable to cocaine addiction while the large majority would be resilient despite extensive drug use. Resilience to drug addiction has long been suspected in humans but could not be firmly established, mostly because it is difficult to control retrospectively for differences in drug self-exposure and/or availability in human drug users. This conclusion has important implications for preclinical research on the neurobiology of cocaine addiction and for future medication development

Anti-relapse neurons in the infralimbic cortex of rats drive relapse-suppression by drug omission cues

Drug addiction is a chronic relapsing disorder of compulsive drug use. Studies of the neurobehavioral factors that promote drug relapse have yet to produce an effective treatment. Here we take a different approach and examine the factors that suppress – rather than promote – relapse. Adapting Pavlovian procedures to suppress operant drug response, we determined the anti-relapse action of environmental cues that signal drug omission (unavailability) in rats. Under laboratory conditions linked to compulsive drug use and heightened relapse risk, drug omission cues suppressed three major modes of relapse-promotion (drug-predictive cues, stress, and drug exposure) for cocaine and alcohol. This relapse-suppression is partially driven by omission cue-reactive neurons, which constitute small subsets of glutamatergic and GABAergic cells, in the infralimbic cortex. Future studies of such neural activity-based cellular units (neuronal ensembles/memory engram cells) for relapse-suppression can be used to identify alternate targets for addiction medicine through functional characterization of anti-relapse mechanisms

Activité nitrate réductase in vitro de jeunes plantules de blé (Triticum aestivum L) cultivées dans les conditions de détermination de la faculté germinative et après amélioration de la nutrition et de l'éclairement

Quand les plantules de blé croissent dans les conditions de détermination de la faculté germinative édictées par l'ISTA (International Seed Testing Association) : sable humidifié par de l'eau déminéralisée, 8 h par jour de lumière faible : 55 μmol photon.m -2.s-1, «milieu clos», leur activité nitrate réductase est très faible. En absence de nitrate, il peut s'agir d'une nitrate réductase constitutive, qui varie peu entre 3 et 12 j de croissance. La présence de KNO3 dans le milieu induit l'activité nitrate réductase qui augmente entre 3 et 6 jours, surtout dans les feuilles, puis reste constante et diminue entre 9 et 12 j; dans ce «milieu clos»; l'augmentation de l'intensité lumineuse, à 200 μmol photon.m-2.s-1, c'est-à-dire au-dessus du point de compensation en lumière, ne provoque pas l'accroissement de l'activité nitrate réductase que l'on observe si les plantules croissent en «milieu ouvert» : dans ce cas, la transpiration est possible et l'apport de nitrate de potassium ou mieux, de solution nutritive équilibrée, est journalier. Trois jours après le semis, l'activité nitrate réductase dans les racines correspond à plus de la moitié de l'activité totale des plantules; dès le 4e j, l'activité nitrate réductase dans la partie aérienne dépasse 50% de l'activité totale; elle atteint 90% au 6 e j quel que soit le traitement.In vitro nitrate reductase activity of wheat (Triticum aestivum L) seedlings grown under various nutrient and light conditions. When wheat seedlings were grown in conformity with ISTA (the International Seed Testing Association) rules ie on sand, deionized water, in a "closed environment" and at a light intensity of 55 μmol photon.m 2.s-1, nitrate reductase activity was very low as a constitutive form. Potassium nitrate induced nitrate reductase activity, which increased from the 3rd to the 6th d of growth, mainly in the leaves, then remained constant and decreased from the 9th to the 12th d. With a "closed environment", increasing irradiation up to 200 μmol photon.m-2.s -1, ie above the light compensation point, did not induce an increase in enzyme activity. In contrast, when seedlings grew in an "open environment", allowing transpiration and with a daily supply of potassium nitrate or better still a complete nutrient solution, activity was very significant. Three d after sowing, enzyme activity was essentially located in the roots. After 4 d of growth, shoot nitrate reductase activity rose to > 50% and attained 90% of whole plant activity on the 6th d