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PubMedDate not supplied

[Electron paramagnetic resonance study of electron transport in photosynthetic systems. VIII. The interplay between two photosystems and kinetics of P700 redox transients under various conditions of flash excitation].

The kinetics P700 redox transients in bean chloroplasts induced by short (t 1/2 = 7 microsecond) flashes of white light has been studied. The flashes were fired in the dark or simultaneously with the continuous background far red light (707 nm). After oxidation of electron transport chain by 707 nm light only 50% of P700+ centres were reduced by photosystem 2 in response to the first flash of saturating intensity. The total reduction of P700+ centres was observed only after two or more saturating flashes. The similar data were obtained for various native photosynthetic systems (bean leaves and leaves of other higher plants). It has been shown that the quantitative difference in P700 behaviour after the first and following flashes may be interpreted in terms of a mechanism of the plastoquinol oxidation by photosystem 1. Twofold oxidation of one molecule of plastoquinol was assumed as its successive oxidation to plastosemiquinone and plastoquinone by different acceptors localized nea the same P700 centre (cytochrome f and plastocyanine). It has been shown that one molecule of plastoquinol was arised due to the interaction of two plastosemiquinones reduced by different P680 centre.

Chloroplasts↗
PubMed1989

Prolactin-lowering ability of (+/-)-idazoxan may be linked to a central noradrenergic-serotonergic interplay.

2-[2-(1,4-benzodioxanyl)-2-imidazoline] (idazoxan) sometimes lowers basal prolactin levels in the male adult rat, but strongly inhibits hyperprolactinemia in suckling rats. A possible antido paminergic drug effect is not involved, due to its inability to modify prolactin release from superfused pituitary in vitro as well as rat haloperidol hyperprolactinemia in vivo. On the contrary, in the rat idazoxan counteracts hyperprolactinemias due to central presynaptic serotonergic neurotransmission increase (5-hydroxytryptophan, D-fenfluramine and fluoxetine) but not those related to direct agonists at 5-hydroxytryptamine (5-HT) receptor (6-chloro-2-[1-piperazinyl] pyrazine, MK 212; 1-(2,5-dimethoxy-4-iodophenyl)2-aminopropane, DOI). (+/-)-Idazoxan does not modify [3H]-5-HT release from isolated hypothalamic synaptosomes. It displays an affinity for alpha-2 adrenergic autoreceptors about 250-fold more than for alpha-2 heteroreceptors located on 5-HT nerve terminals in the central nervous system (pA2 value 9.99, equivalent to a Kb of 0.1 nM vs. pA2 7.60 equivalent to a Kb of 2.5 nM). The noradrenergic outflow selectively induced by idazoxan in the brain may negatively modulate the 5-HT release from the relevant nerve endings, thus preventing prolactin release due to an activation of presynaptic serotonergic axons induced both physiologically (lactation) and pharmacologically (5-hydroxytryptophan, D-fenfluramine and fluoxetine) without influencing hyperprolactinemias related to a direct activation of serotonergic receptors (MK 212 and DOI). Other blocking agents, strong but less selective than (+/-)-idazoxan for noradrenergic brain neurotransmission, do not modify or increase blood prolactin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

Interplay among cardiac chambers. Left and right ventricular performance during changes in contractility, afterload and during simultaneous atrio-ventricular contraction.

1. Only a slight increase in stroke volume is observed during a selective left-sided inotropic stimulation of the in situ pig heart. Decreased left ventricular preload during left-sided inotropic stimulation reduces activation of the Frank-Starling mechanism and hence explains the rather small increase in stroke volume. We suggest that left-sided inotropic stimulation redistributes blood from the pulmonary circulation toward the systemic circulation causing a fall in pulmonary artery pressure and increased right ventricular output because of this afterload-reduction. 2. A rise in stroke volume during selective right-sided inotropic stimulation is not attenuated by a concomitant reduction in right ventricular preload. On the contrary, right ventricular preload rises in response to inotropic stimulation of the right atrium. Right-sided inotropic stimulation redistributes blood toward the pulmonary vascular bed and the left side of the heart. Left ventricular function is improved by this redistribution. 3. Both left ventricular end-systolic and end-diastolic volumes are better maintained by thoracic aortic occlusion during left-sided inotropic stimulation than at control inotropy. The concomitantly better preserved dimensions in the right ventricle can be explained by reduced pressure in the pulmonary circulation and a decrease in right-ward septal bulging. The rise in stroke volume by aortic occlusion during intravenous isoproterenol infusion is mainly due to a greater redistribution volume than at control inotropy. 4. Prolongation of the diastolic interval may reduce the end-diastolic pulmonary artery pressure to such an extent that right atrial contraction could eject blood into the pulmonary artery during late ventricular diastole.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The interplay between pathological organizations and the paranoid-schizoid and depressive positions.

I have presented clinical material to illustrate how a pathological organization can be considered to exist in an equilibrium with the paranoid-schizoid and depressive positions. While making use of paranoid-schizoid mechanisms such as primitive splitting and projective identification, the defensive structure is highly organized and held together by narcissistic intrapsychic relationships in which perverse gratification plays an important role. This organization of defences seems to be designed to produce a place of real or illusionary safety from the anxieties experienced in the other two positions. All individuals fluctuate in the defences they employ and hence can be thought of as moving between these organizations and the other two positions. They consequently demonstrate some evidence of paranoid-schizoid level function and also of the existence of pathological organizations even if they may function in a relatively mature way at other times and in other settings. In some patients however the pathological organization dominates the personality and leads to analyses which become fixed and stuck. It is argued that a recognition of these organizations of defences enables the analyst to orient himself more accurately to the clinical material and hence to address himself to the patient at a level he can understand.

Adult↗
PubMed1986

Interplay between lipids and viral glycoproteins during hemolysis and fusion by influenza virus.

Since mixtures of lipids alone are known to elicit membrane fusion without participation of fusion proteins, the role of viral lipids in the so-called virus-induced hemolysis and cell fusion has been investigated, using as a model the fowl plague virus (influenza A/FPV/Rostock/H7N1). The experiments were planned in a way that allowed quantitative modification of viral lipids without changing envelope glycoproteins. Under the conditions employed, cholesterol oxidase of Nocardia erythropolis and phospholipase C of Bacillus cereus were shown to completely modify their substrates in the virus without altering virus-associated hemagglutinating and neuraminidase activities. It was found with such enzyme treatment that virus-induced hemolysis and cell fusion are greatly influenced by cholesterol and phospholipids of the envelope. It became clear, that hemolysis and fusion are differently dependent on the nature of lipid components even though mediated by the same viral glycoproteins.

Animals↗