Site,trigger, quenching mechanism and recovery of non-photochemical quenching in cyanobacteria: recent updates

Femtosecond transient absorption was used to study excitation decay in monomeric and trimeric cyanobacterial Photosystem I (PSI) being prepared in three states: (1) in aqueous solution, (2) deposited and dried on glass surface (either conducting or non-conducting), and (3) deposited on glass (conducting) surface but being in contact with aqueous solvent. The main goal of this contribution was to determine the reason of the acceleration of the excitation decay in dried PSI deposited on the conducting surface relative to PSI in solution observed previously using time-resolved fluorescence (Szewczyk et al., Photysnth Res 132(2):111–126, 2017). We formulated two alternative working hypotheses: (1) the acceleration results from electron injection from PSI to the conducting surface; (2) the acceleration is caused by dehydration and/or crowding of PSI proteins deposited on the glass substrate. Excitation dynamics of PSI in all three types of samples can be described by three main components of subpicosecond, 3–5, and 20–26 ps lifetimes of different relative contributions in solution than in PSI-substrate systems. The presence of similar kinetic components for all the samples indicates intactness of PSI proteins after their deposition onto the substrates. The kinetic traces for all systems with PSI deposited on substrates are almost identical and they decay significantly faster than the kinetic traces of PSI in solution. We conclude that the accelerated excitation decay in PSI-substrate systems is caused mostly by dense packing of proteins.     

Influence of parathyroidectomy on liver glycogen in rats treated with carbon tetrachloride

Carbon tetrachloride (CCl4) brings about a rise in cytosolic free calcium which may lead to glycogen mobilization. Therefore, glycogen and glucose-6-phosphatase (G-6-pase) levels in the liver of parathyroidectomized (PTX) rats following CCl4 treatment have been estimated. CCl4 depletes both glycogen and G-6-pase levels in the liver. PTX followed by CCl4 administration, however, fails to restore liver glycogen and G-6-pase levels. The results suggest that neither cytosolic Ca2+ nor phospholipase A2 mediation is needed for glycogen mobilization, however, glucocorticoid intervention might have a role in such mechanisms.     

Prey concealment and spatiotemporal patrolling behaviour of the Indian tree ant Oecophylla smaragdina (Fabricius)

Summary: Oecophylla smaragdina workers conceal prey with leaves and twigs on discovering large prey on their ground territory. The prey concealment behaviour occurs concurrently with prey capture and killing. Ants were observed conducting spatiotemporal patrolling around large prey. The garden lizard Calotes versicolor and at least two predatory ant species were found to forage in the same area as O. smaragdina. It is suggested that the prey concealment behaviour of Oecophylla may be a strategy to prevent prey detection by vertebrate predators which use vision to prey on similar large prey species.     

Distribution of gonadotropin-releasing hormone-like peptides in the brain during development of juvenile male Rana esculenta

Summary The distribution and density of cell bodies and fibers immunoreactive to GnRH-like peptides were investigated in the brain of male juvenile frogs (Rana esculenta) during postmetamorphic development. An immunohistochemical technique was used, involving antisera raised against 4 variants of GnRH: mammalian GnRH, chicken GnRH-I, chicken GnRH-II and salmon GnRH. A comparison of the immunohistochemical distribution at 8 different developmental stages shows that the maximum density of immunoreactive-GnRH elements, and the full distributional complexity of this system, is attained at the completion of spermatogenesis. Immunoreactive-GnRH cell bodies first appear in the anterior preoptic area during the metamorphic climax, and then appear sequentially in the medial septal area, tegmentum and, lastly, in the retrochiasmatic area and olfactory bulb when immunoreactive-fibers also reach the cerebellum. The GnRH system reacts positively to antisera for all 4 GnRH variants, but immunoreactivity for chicken GnRH-I is the weakest.