Pheophytin-mediated energy storage of photosystem II particles detected by photoacoustic spectroscopy

The photoacoustic (PA) characteristics (energy storage and heat dissipation) of photosystem II (PSII) core-enriched particles from barley were studied (i) in conditions where there was electron flow, i.e., in the presence of a combination of the electron acceptor K₃ Fe (CN)₆, referred to as FeCN, and the electron donor diphenylcarbazide (DPC), and (ii) in conditions where electron flow was suppressed, i.e., in the absence of FeCN and DPC. The experimental data show that a decrease of heat dissipation with a minimum at 540 nm can be interpreted as energy storage resulting from the presence of pheophytin (Pheo) in the PSII particles. On account of the capability of the PA method to measure the energy absorbed by the chromophores which is converted to heat, it is suggested that the PA detection of Pheo present in the PSII complex will permit to clarify the function of processes involving non-radiative relaxation of excited states in P680-Pheo-Q_A interactions.Abbreviations -Car -Carotene - Chl Chlorophyll - DPC Diphenylcarbazide - EPR Electron Paramagnetic Resonance - FeCN potassium ferricyanide - HEPES N-2-hydroxyethylenepiperazine-N-2-ethanesulfonate - P680 reaction center of PSII - PA Photoacoustic - Pheo pheophytin - PSI photosystem I - PSII photosystem II - Q_A primary electron acceptor of PSII     

3'-5' cyclic-guanosine monophosphate increase in rat brain hippocampus after gamma-hydroxybutyrate administration. Prevention by valproate and naloxone

An increase (123%) of cyclic GMP (cGMP) was observed in the hippocampus of the rat killed by microwave irradiation 45 min after administration of 500 mg/kg gamma-hydroxybutyrate (GHB) IP. This increase is time and dose dependent. No modification in cyclic nucleotide content was observed in striatum and in cerebellum. As the role of GHB has been implicated in neurotransmission, the fact that this compound increases cyclic GMP accumulation in hippocampus in vivo may represent a mechanism by which the actions of GHB are mediated at the cellular level. Valproate (400 mg/kg) or naloxone (10 mg/kg) pretreatment completely abolish the cGMP increase due to GHB. A GABAergic and/or opiate phenomenon may be involved in the mechanism of GHB induced increase of cGMP.     

Influence of adrenergic receptors on ovarian progesterone secretion in the pseudopregnant cat and oestradiol secretion in the oestrous cat

The infusion of isoprenaline or propranolol into the abdominal aorta of the pseudopregnant cat caused an increase or decrease respectively in the ovarian progesterone secretion rate. These observations suggest that the sympathetic innervation of the ovary has a physiological influence on normal progesterone secretion, and this mechanism may explain stress-related increases in progesterone concentrations. The infusion of isoprenaline or propranolol after the stimulation of follicular growth had no consistent or convincing effect on oestradiol secretion.     

Further studies on the morphology of the Triviidae (Gastropoda: Prosobranchia) with emphasis on species from southern Africa

Aspects of the morphology of II species of Triviidae are described, including the living animal, shell, radula, mantle complex, central nervous system and reproductive system. Interspecific differences in radular morphology are important in distinguishing closely allied species. Trivia aperta, T. costata and T. verhoeft are protandric hermaphrodites while T. caluariola, T. neglccta, T. pellucidula, T. rubra, T. solandri and T. suavis are gonochoric. The elaboration of the receptaculum seminis varies between species. In T. aperta, T. calvariola, T. neglecta and T. who& the receptaculum is undivided while in T. costafa, T. pellucidula, T. solandri and T. suavis there are two or more lobes of the receptaculum.     

Dynamics of immunoglobulins and immunocompetent lymphocytes in guinea pigs with experimental ascariasis

The paper presents data on variations in the level of serous immunoglobulins (Ig M and Ig G classes), immunocompetent T- and B-lymphocytes in lymphoid organs (spleen, mesenteric, portal and mediastinal lymph nodes) and specific antiparasitic antibodies in guinea pigs during the dynamics of experimental ascariasis.     

The right ventricular working heart preparation

An isolated working rat heart preparation was modified to study right ventricular (RV) performance. All hearts were perfused with a Krebs-Henseleit bicarbonate buffer via a Langendorff column at 90 mm Hg. Right atrial filling (preload) was varied by raising a buffer reservoir from 5 cm below to 10 cm above the right atrium while pulmonary artery outflow resistance remained fixed. RV systolic pressure and the maximum rise and decrease in pressure development (+/- dP/dt) were measured via a catheter in the RV. Cardiac output was collected with a catheter placed in the pulmonary artery. One group of hearts, monitored at a fixed preload (0 cm H2O) for 2 hr, and another group of hearts, in which two ventricular function curves were performed, demonstrated the stability and reproducibility of the preparation. Additionally, the ability of this preparation to measure changes in inotropy was studied. A negative inotropic effect was measured after verapamil (5 X 10(-8) M) treatment. Positive dP/dt showed the greatest depression (30%) and was significantly lower at every preload. A positive inotropic effect was demonstrated by reducing the buffer Ca2+ concentration to 1.9 mM for the first work curve followed by an addition of Ca2+ (2.8 mM final concentration) or ouabain (5 X 10(-5) M) for the second work curve. Again, the greatest effect was found in the dP/dt measurements (elevated by 20 and 30%, respectively). Thus, this preparation manifests qualities similar to those used in studying the left ventricle and allows investigation of various cardiac diseases which may affect RV pump function.     

Catecholamine content and acetylcholinesterase activity in the brain of rats exposed to lasers

The catecholamine content was quantitated and acetylcholinesterase activity determined in rat brain locally exposed to laser radiation. It was shown that the adrenaline/noradrenaline ratio changed in the tissues under study and the cholinergic system was involved in the abscopal effect of laser radiation.     

Relative biological effectiveness (RBE) of neutrons produced by 50 MeV deuterons and by 34, 45, 65 and 75 MeV protons

RBE of p(34) + Be, p(45) + Be, p(65), + Be, p(75) + Be and d(50) + Be neutron beams produced at the cyclotron "Cyclone" of Louvain-la-Neuve were measured. The biological criterion was the regeneration of the crypts of the intestinal mucosa (50 regenerated crypts per circumference) after abdominal irradiation in mice. Taking the p(65) + Be neutrons as reference, RBE values were found equal to 1.12, 1.07, 1.00 (Ref.), 0.96 and 1.02 respectively. These results are consistent with those published for cell lethality in vitro. However, the RBE variation is smaller than this previously obtained in the laboratory for growth inhibition in Vicia faba.