Light-Related Photosynthetic Characteristics of Lotic Macroalgae

Photosynthetic characteristics in response to irradiance were analysed in 42 populations of 33 macroalgal species by two distinct techniques (chlorophyll fluorescence and oxygen evolution). Photosynthesis–irradiance (PI) curves based on the two techniques indicated adaptations to low irradiance reflected by low saturation values, high to moderate values of photosynthetic efficiency (α) and photoinhibition (β), for Bacillariophyta and Rhodophyta, which suggests they are typically shade-adapted algae. In contrast, most species of Chlorophyta were reported as sun adapted algae, characterized by high values of I _k and low of α, and lack of or low photoinhibition. Cyanophyta and Xanthophyta were intermediate groups in terms of light adaptations. Photoinhibition was observed in variable degrees in all algal groups, under field and laboratory conditions, which confirms that it is not artificially induced by experimental conditions, but is rather a common and natural phenomenon of the lotic macroalgae. Low values of compensation irradiance (I _c) were found, which indicate that these algae can keep an autotrophic metabolism even under very low irradiances. High ratios (>2) of photosynthesis/respiration were found in most algae, which indicates a considerable net gain. These two physiological characteristics suggest that macroalgae may be important primary producers in lotic ecosystems. Saturation parameters (I _k and I _s) occurred in a relatively narrow range of irradiances (100–400 μmol photons m^?2s^?1), with some exceptions (higher in some filamentous green algae or lower in red algae). These parameters were way below the irradiances measured at collecting sites for most algae, which means that most of the available light energy was not photochemically converted via photosynthesis. Acclimation to ambient PAR was observed, as revealed by lower values of I _k and I _cand higher values of α and quantum yield in algae from shaded streams, and vice versa. Forms living within the boundary layer (crusts) showed responses of shade-adapted species and had the highest values of P _max, α and quantum yield, whereas the opposite trend was observed in gelatinous forms (colonies and filaments). These results suggests adaptation to the light regime rather than functional attributes related to the growth form.     

Pulse ENDOR and density functional theory on the peridinin triplet state involved in the photo-protective mechanism in the peridinin-chlorophyll a-protein from Amphidinium carterae

The photoexcited triplet state of the carotenoid peridinin in the Peridinin-chlorophyll a-protein of the dinoflagellate Amphidinium carterae has been investigated by pulse EPR and pulse ENDOR spectroscopies at variable temperatures. This is the first time that the ENDOR spectra of a carotenoid triplet in a naturally occurring light-harvesting complex, populated by energy transfer from the chlorophyll a triplet state, have been reported. From the electron spin echo experiments we have obtained the information on the electron spin polarization dynamics and from Mims ENDOR experiments we have derived the triplet state hyperfine couplings of the α- and β-protons of the peridinin conjugated chain. Assignments of β-protons belonging to two different methyl groups, with a_iso = 7.0 MHz and a_iso = 10.6 MHz respectively, have been made by comparison with the values predicted from density functional theory. Calculations provide a complete picture of the triplet spin density on the peridinin molecule, showing that the triplet spins are delocalized over the whole π-conjugated system with an alternate pattern, which is lost in the central region of the polyene chain. The ENDOR investigation strongly supports the hypothesis of localization of the triplet state on one peridinin in each subcluster of the PCP complex, as proposed in [Di Valentin et al. Biochim. Biophys. Acta 1777 (2008) 186-195]. High spin density has been found specifically at the carbon atom at position 12 (see Fig. 1B), which for the peridinin involved in the photo-protective mechanism is in close contact with the water ligand to the chlorophyll a pigment. We suggest that this ligated water molecule, placed at the interface between the chlorophyll-peridinin pair, is functioning as a bridge in the triplet-triplet energy transfer between the two pigments.     

Influence of training in the dark or light phase on physiologic and metabolic parameters of Wistar rats submitted to aerobic exercise

Light and dark phase training may influences rodents’ physiologic parameters because these animals have nocturnal habits. Thus, we verify the effects of the training in different photoperiods on metabolism and corporal composition of rats. Eighteen rats were divided into three groups – G1: non-trained; G2: trained in the light phase; G3: trained in the dark phase. Rats were allowed to swim for 60 min, five times per week during six weeks. Trained animals presented a smaller weight gain and fat percentage in carcass. Rats of G3 increased gastrocnemius relative weight. The adipocyte diameter of G3 rats was smaller than the other groups. The levels of the total cholesterol, low-density proteins, and triacylglycerols were decreased in animals of G2 while the glycemia was increased. Training in light phase provided more alterations in the blood biochemical profile while the training in the dark increased the gastrocnemius weight and decreased the diameter of the adipocyte.     

Conversion of glutathione to glutathione disulfide, a catalytic function of gamma-glutamyl transpeptidase.

A purification procedure, based on that previously used for rat kidney gamma-glutamyl transpeptidase, was used for the purification of glutathione oxidase (which converts glutathione to gluthathione disulfide). The two activities co-purified, the ratio of the activities remaining constant through all steps of the isolation procedure. The purified enzyme was separable into 12 isozymic species by isoelectric focusing. All 12 isozymes exhibited a constant ratio of transpeptidase to glutathione oxidase activities, strongly supporting the conclusion that conversion of glutathione to glutathione disulfide is a catalytic function of gamma-glutamyl transpeptidase. Modulation of oxidase activity by inhibitors and acceptor substrates of transpeptidase is discussed in relation to the possible glutathione binding sites involved in gamma-glutamyl transfer and oxidase activities of the enzyme.     

Effect of ubiquinol supplementation on biochemical and oxidative stress indexes after intense exercise in young athletes

Objectives: Physical exercise significantly impacts the biochemistry of the organism. Ubiquinone is a key component of the mitochondrial respiratory chain and ubiquinol, its reduced and active form, is an emerging molecule in sport nutrition. The aim of this study was to evaluate the effect of ubiquinol supplementation on biochemical and oxidative stress indexes after an intense bout of exercise.

Methods: 21 male young athletes (26?+?5 years of age) were randomized in two groups according to a double blind cross-over study, either supplemented with ubiquinol (200?mg/day) or placebo for 1 month. Blood was withdrawn before and after a single bout of intense exercise (40 min run at 85% maxHR). Physical performance, hematochemical parameters, ubiquinone/ubiquinol plasma content, intracellular reactive oxygen species (ROS) level, mitochondrial membrane depolarization, paraoxonase activity and oxidative DNA damage were analyzed.

Results: A single bout of intense exercise produced a significant increase in most hematochemical indexes, in particular CK and Mb while, on the contrary, normalized coenzyme Q₁₀ plasma content decreased significantly in all subjects. Ubiquinol supplementation prevented exercise-induced CoQ deprivation and decrease in paraoxonase activity. Moreover at a cellular level, in peripheral blood mononuclear cells, ubiquinol supplementation was associated with a significant decrease in cytosolic ROS while mitochondrial membrane potential and oxidative DNA damage remained unchanged.

Discussion: Data highlights a very rapid dynamic of CoQ depletion following intense exercise underlying an increased demand by the organism. Ubiquinol supplementation minimized exercise-induced depletion and enhanced plasma and cellular antioxidant levels but it was not able to improve physical performance indexes or markers of muscular damage.     

Trace element determination in humans

With the present study, we intend to verify the utility of hair as diagnostic tool for trace element analysis, to substitute, perhaps, conventional materials, such as blood serum. Blood and hair were collected from male individuals (n=107) aged 20–59 y. Determinations of Cu and Zn concentrations were performed with atomic absorption spectrometry. An influence of age on Zn in hair has been found, with significantly different values before and after age 30 y. There is no correlation between Cu concentrations in hair and in serum, and a positive one (r=0.3554,p<0.05) between Zn levels in hair and in serum. No association between Zn and Cu levels in hair has been demonstrated; on the contrary, these elements have a moderate positive correlation in serum (r=0.3586,p<0.01). The data indicate that hair may represent an additional analytical material for Cu and Zn to complement blood serum.