Curated Optogenetic Publication Database

Abstract: The phytochrome photoreceptor family directs plant gene expression by switching between biologically inactive and active conformers in response to the sequential absorption of red and farred photons. Several intermediates that act late in the phytochrome signalling pathway have been identified, but fewer have been identified that act early in the pathway. We have cloned a nuclear basic helix-loop-helix protein, PIF3, which can bind to non-photoactive carboxy-terminal fragments of phytochromes A and B and functions in phytochrome signalling in vivo. Here we show that full-length photoactive phytochrome B binds PIF3 in vitro only upon light-induced conversion to its active form, and that photoconversion back to its inactive form causes dissociation from PIF3. We conclude that photosensory signalling by phytochrome B involves light-induced, conformer-specific recognition of the putative transcriptional regulator PIF3, providing a potential mechanism for direct photoregulation of gene expression.

Abstract: Divalent cations induce the aggregation of chromaffin granule ghosts (CG membranes) at millimolar concentrations. Monovalent cations produce the same effect at 100-fold higher concentrations. The kinetics of the dimerization phase were followed by light-scattering changes observed in stopped-flow rapid mixing experiments. The rate constant for Ca2+-induced dimerization (kapp) is 0.86-1.0 x 10(9) M-1sec-1, based on the "molar" vesicle concentration. This value is close to the values predicted by theory for the case of diffusion-controlled reaction (7.02 x 10(9) M-1sec-1), indicating that there is no energy barrier to dimerization. Arrhenius plots between 10 degrees and 42 degrees C support this; the activation energy observed, +4.4 Kcal, is close to the value (4.6-4.8 Kcal) predicted for diffusion control according to theory. Artificial vesicles prepared from CG lipids were also found to have cation-induced aggregation, but the rates (values of kapp) were less than 1/100 as large as those with native CG membranes. Also, significant differences were found with respect to cation specificity. It is concluded that the slow rates are due to the low probability that the segments of membrane which approach will be matched in polar head group composition and disposition. Thus large numbers of approaches are necessary before matched segments come into aposition. The salient features of the chromaffin granule membrane aggregation mechanism are as follows: (a) In the absence of cations capable of shielding and binding, the membranes are held apart by electrostatic repulsion of their negatively charged surfaces. (b) The divalent and monovalent cation effects on aggregation are due to their ability to shield these charges, allowing a closer approach of the membrane surfaces. (c) The major determinants of the aggregation rates of CG membranes are proteins which protrude from the (phospholipid) surface of the membrane and serve as points of primary contact. Transmembrane contact between these proteins does not require full neutralization of the surface charge and surface potential arising from the negatively charged phospholipids. (d) After contact between proteins is established, the interaction between membranes can be strengthened through transmembrane hydrogen bonding of phosphatidyl ethanolamine polar head groups, divalent cation-mediated salt bridging, and segregation of phosphatidylcholine out of the region of contact.

Abstract: Abstract not available.

Abstract: A case of an 11-months-old girl with traumatic occlusion of supraclinoid portion of internal carotid artery is reported. The patient died about 22 hours after the craniocerebral trauma.

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Abstract: RMI 61 140, RMI 61 144 and RMI 61 280 are newly synthetized N-[8-R-dibenzo(b,f)oxepin-10-yl]-N'-methyl-piperazine-maleates which show interesting psychopharmacologic effects. This work contains the results of a study performed with these three compounds, in order to demonstrate their neuropsycholeptic activity in comparison with chloropromazine (CPZ) and chlordiazepoxide (CPD). The inhibition of motility observed in mice shows that the compounds reduce the normal spontaneous motility as well as the muscle tone. The central-depressant activity is evidenced by increased barbiturate-induced sleep and a remarkable eyelid ptosis can also be observed. Our compounds do not show any activity on electroshock just as do CPZ and CPD. As to the antipsychotic outline, our compounds show strong reduction of lethality due to amphetamine in grouped mice and a strong antiapomorphine activity. They show also an antiaggressive effect and an inhibitory activity on avoidance behaviour much stronger than CPZ. We have also found extrapyramidal effects, as catalepsy, common to many tranquillizers of the kind of the standards used by us. As for vegetative phenomena, the compounds show hypotensive dose related action ranging from moderate to strong, probably due to an a-receptor inhibition. Adrenolytic activity against lethal doses of adrenaline, antiserotonin and antihistaminic effects, as well as other actions (hypothermia, analgesia, etc.) confirm that RMI 61 140, RMI 61 144 and RMI 61 280 are endowed with pharmacologic properties similar and more potent than those of CPZ. Studies on the metabolism of brain catecholamines show that they are similar to CPZ, although with less effect on dopamine level.

Abstract: Abstract not available.