Energy transfers from photosystem II to photosystem I in Cryptomonas rufescens (Cryptophyceae).

In Cryptomonas rufescens (Cryptophyceae), phycoerythrin located in the thylakoid lumen is the major accessory pigment. Oxygen action spectra prove phycoerythrin to be efficient in trapping light energy. The fluorescence excitation spectra at -196 degrees C obtained by the method of Butler and Kitajima (Butler, W.L. and Kitajima, M. (1975) Biochim. Biophys. Acta 396, 72-85) indicate that like in Rhodophyceae, chlorophyll a is the exclusive light-harvesting pigment for Photosystem I. For Photosystem II we can observe two types of antennae: (1) a light-harvesting chlorophyll complex connected to Photosystem II reaction centers, which transfers excitation energy to Photosystem I reaction centers when all the Photosystem II traps are closed. (2) A light-harvesting phycoerythrin complex, which transfers excitation energy exclusively to the Photosystem II reaction complexes responsible for fluorescence at 690 nm. We conclude that in Cryptophycease, phycoerythrin is an efficient light-harvesting pigment, organized as an antenna connected to Photosystem II centers, antenna situated in the lumen of the thylakoid. However, we cannot afford to exclude that a few parts of phycobilin pigments could be connected to inactive chlorophylls fluorescing at 690 nm.

Correlated influence of cation concentration and excitation intensity on PS II activity-I. Influence of high salt concentration on spinach chloroplast activity.

A correlated influence of cation concentration and excitation energy level on PS II Abbreviations: AMPD = 2-amino-2-methyl-1,3-propanediol; DCIP = 2-6 dichlorophenol indophenol; DCIPH2 = DCIP in reduced state; DCIPr = rate of DCIP-reduction; DCMU = 3-(3,4 dichlorophenyl)1-1 dimethyl-urea; Fv = variable fluorescence; Fcat = Fv in the presence of added cations; Ft = Fv without added cations; HEPES = N-2-hydroxyethylpiperazine N\t'2-sulfonic acid; PS II = photosystem II; Vcat = DCIPr in presence of added cations; Vt = DCIPr without added cations. activity is demonstrated.In low light conditions (under 60 Wm(-2)) Mg(++) effect on DCIP reduction rate (DCIPr) saturates at rather low concentrations (2-10 mM). Higher concentrations induce a quenching of the effect, as already observed by several authors. In high light conditions (1000 Wm(-2)) however, Mg(++) is increasingly effective on DCIPr up to concentrations of 200 mM.Na(+) induced variations of DCIPr are weak in low light conditions and slightly positive for 100-600 mM in strong light; no quenching occurs.Modifications in variable fluorescence do not follow those of DCIPr in all cases, especially in high light.These results allow us to distinguish three different effects of cations on the photochemistry of PS II: one on the spill-over, another on the turnover rate of the centers and the last on the cation exchange through the thylakoid membrane.

Correlated influence of cation concentration and excitation intensity on PS II activity-II. Comparative study between green plant and brown-alga chloroplasts.

A preparation of photochemically active chloroplasts of Fucus was added to a low-salt medium with high osmolarity (HEPES AMPD buffer, 1M sorbitol). The rate of DCIP reduction (DCIPr) and the variable fluorescence (Fv) of these phaeoplasts were measured and compared with the same activities in spinach chloroplasts. A study of the influence of mono- and divalent-cations showed that salt effects on PS II activity also exist in Fucus. (i) Mg(++) action on Fv is similar, although noticeably weaker in Fucus than in spinach chloroplasts. (ii) Na(+) has no effect on Fv of Fucus chloroplasts, but its influence on DCIPr is more pronounced than in spinach. (iii) Mg(++) influence on DCIPr is largely dependent upon excitation energy. In subsaturating light (100\2-1000 W m(\t-2)), Mg(++) stimulation increases up to 100 mM, almost doubling the level. In very low wight conditions (3Wm(\t02)), however, this stimulation saturates at about 10 mM; higher concentrations are no longer effective but do not quench DCIPr noticeably, unlike the case in spinach. Therefore, cations act through similar pathways on Fucus as on spinach isolated chloroplasts but the effects on PS II centers are preponderant in Fucus whereas the modifications in non-radiative decay or pigment array size are weaker.

Chlorophyll fluorescence transients from the diatom Phaeodactylum tricornutum: relative rates of cyclic phosphorylation and chlororespiration.

In Phaeodactylum tricornutum cells kept 30 min in the dark, induction of fluorescence showed the well-known levels OIDPSMT. The decrease of MT was the most important when the intensity of excitation light was high. It was mainly due to the photochemical quenching. After addition of DCMU (2 to 20 µM), a quenching qE was still observed: this quenching, cancelled by NH4Cl (2 to 20 mM) is attributed to ΔpH. This qE was also inhibited by antimycin, an inhibitor of cyclic phosphorylation and may be of chlororespiration above plastoquinones. Anaerobiosis also decreased it. We can infer that chlororespiration also plays a part in the formation of the ΔpH in the presence of DCMU. After 30 mn of preillumination in red light, the levels P and M were lower and the quenching in presence of DCMU was no more observed: thus, neither the chlororespiration nor the cyclic phosphorylation were active, unless the activity of ATPase was much more important. So, in diatoms, one at least of the above cited phenomena can be modulated by light.

State transitions or delta pH-dependent quenching of photosystem II fluorescence in red algae.

Fluorescence changes attributed to state transitions have been shown to exist in phycobilisome-containing organisms. Contradictory conclusions have been derived from studies about the mechanism of state transitions carried out either in cyanobacteria or in red algae. In this paper, fluorescence changes induced by light 1 and light 2 are reinvestigated in a unicellular red alga, Rhodella violacea, by performing 77 K fluorescence spectra and fluorescence yield measurements at room temperature in the presence of uncouplers and inhibitors of the electron transfer. We show that transfer of light 1-adapted cells to light 2 (green light) induces a large quenching of photosystem II which is suppressed by subsequent incubation in light 1 (far-red or blue light). The level of the photosystem I-related fluorescence does not change during these transfers. We demonstrate that the large quenching of photosystem II induced by low intensities of green light is completely suppressed by addition of NH4Cl, an uncoupler that inhibits ATP synthesis by canceling the delta pH across the membrane. DCCD, which is an inhibitor of the ATPase that swells the delta pH, maintains the quenched state even under light 1 illumination. The opposite effects of DCMU and DBMIB on state transitions are demonstrated to be due to a suppression (by DCMU) or maintenance (by DBMIB) of the delta pH and not to change in the redox state of the plastoquinone. We conclude that, in R. violacea, the fluorescence change commonly associated with state 2 transition is in fact a delta pH-dependent quenching. This type of quenching has always been associated with near-saturating light intensities. Here, we show that very low intensities of a light that activates only the photosystem II induce a delta pH across the membrane that is not dissipated since the ATPase is not activated. The delta pH is dissipated only under conditions in which the photosystem I turns, confirming that the thioredoxin must be reduced to activate the ATPase. We suggest that the fluorescence changes, induced by various light conditions, in cyanobacteria and red algae could be associated with different phenomena.

[The sex life of paraplegics and sociological aspects]. / Santé sexuelle des paraplégiques et aspects sociologiques.

700 able-bodied subjects were interviewed on their views concerning the sexual life of paraplegics. Results of this study, which was not carried out on a national level, are reported. The need for such a study stemmed from a previous inquiry in paraplegics. The different answers are analyzed. They mirror the scope of the problem and point out that the struggle against "human barriers" should be a concern for practitioners.

Ultrasonographic anatomy and diagnosis of fetal uropathies affecting the upper urinary tract. II. Nonobstructive uropathies.

The authors describe the ultrasonographic anatomy and semiology of allowing detection of the main types of fetal non-obstructive uropathies. The results of the author's personal experience in this domain are compared to data from the literature. Differential features of the uropathies are given and the limitations and practical significance of prenatal and postnatal ultrasonography are discussed.

Ultrasonographic anatomy and diagnosis of fetal uropathies affecting the upper urinary tract. I. Obstructive uropathies.

The authors describe the ultrasonographic anatomy and semiology of allowing detection of the main types of fetal uropathies. The results of the author's personal experience in this domain are compared to data from the literature. Differential features of the uropathies are given and the limitations and practical significance of prenatal and postnatal ultrasonography are discussed.