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G Zucchelli

Publications and source records attributed to G Zucchelli.

47 records · Page 3Linked to original sources
PubMed1993

Distribution of the chlorophyll spectral forms in the chlorophyll-protein complexes of photosystem II antenna.

The chlorophyll-protein complexes that form the antenna system of photosystem II have been purified and analyzed in terms of the commonly observed chlorophyll spectral forms. With the exception of chlorophyll b, which is known to be associated with the complexes comprising the outer antenna (LHCII, CP24, CP26, CP29), the spectral forms occur with similar absorption maxima and are present in rather similar amounts in each of the antenna complexes. On the basis of the published chlorophyll stoichiometries for the complexes in photosystem II antenna, the distribution of the spectral forms in a "reconstituted" antenna has been determined. These data were used to calculate the equilibrium population of excited states within the various chlorophyll-protein complexes within photosystem II. This was compared with the light absorption capacity of each of the complexes in the "reconstituted" antenna. The ratio of these two parameters (excited-state equilibrium distribution/absorption capacity) was determined to be 1.21 for the inner (core) antenna and 0.88 for LHCII. The standard free energy change for exciton transfer from the outer to the inner antenna was calculated to be -0.17 kcal mol-1. It is concluded that the photosystem II antenna is arranged as a very shallow funnel.

Chlorophyll↗
PubMed1991

[Functional PMN defects in young periodontal patients].

Peripheral blood polymorfonuclear leukocytes (PMN) are activated by the contact with opsonized bacteria. Metabolic activation of PMN is associated with a remarkable increase in the respiratory burst and generates high energy oxygen compounds which are responsible for the bactericidal activity of neutrophils and for their ability to produce luminol-dependent chemiluminescence (CL). The CL phenomenon is measured by an automated and computerized photoluminometer (Berthold LB950) in whole blood, stimulated with opsonized zymosan. This whole blood method of CL has been applied to the investigation of PMN functional defects in early-onset periodontopatic patients.

Adolescent↗
PubMed1991

Enhanced superoxide production with no change of the antioxidant activity in gingival fluid of patients with chronic adult periodontitis.

In the gingival crevicular fluid (GCF) of control and chronic adult periodontitis (CAP) patients there is a spontaneous release of O2- radicals from polymorphonuclear leukocytes (PMN). The addition of the exogenous stimuli phorbol myristate acetate (PMA) decreased the O2-. formation in control GCF, while in CAP patients produced a marked enhancement of O2-. generation. The circulating PMN of control subjects did not show a spontaneous O2-. formation, differently from CAP patients. On the contrary, a similar O2-. production was measured when the circulating PMN were stimulated with PMA. Moreover, the antioxidant activity measured in 10 microliters of cell free gingival supernatant (GS) of control and CAP patients had the same values by inhibiting 12.6% and 18.9% respectively of the O2- formation supported by a xanthine/xanthine oxidase system. Probably, the protective or destructive effect of PMN in GCF of CAP patients depends on the variations of the rate of O2- formation in respect to the intrinsic antioxidant property of GS.

Adult↗
PubMed1989

[Periodontal disease and crevicular neutrophils. Role of superoxide radicals].

One early biochemical process in PMN activation is the stimulation of the NADPH oxidase membrane enzyme, which produces a flux of superoxide radicals, directed towards the extracellular place. These radicals initiate bacterial destruction; however they can react against the periodontal tissue and lead to its destruction, either when too many of them are produced, or when they are not adequately neutralized by the antioxidant activity of the gingival fluid. Striking a proper balance between the activation state of crevicular PMN and the antioxidant activity of the gingival fluid may be a critical factor in determining whether PMN response to plaque bacteria is either protective or destructive for the parodontium.

Adult↗
PubMed1989

[Polymorphonuclear neutrophilic granulocytes and the defense and damage of periodontal tissues].

The relationship of neutrophil to the periodontal tissue can be equated to the image of a double-edged blade. The role of the polymorphonuclear cells in the containment of gingival bacteria and their products must be weighed against the localized tissue destruction that may be due to the extracellular release of lysosomal enzymes and oxygen derived radicals. It seems reasonable to suggest that the role of neutrophils in the gingival tissue is primarily a defensive one. Therefore, several factors such as the entity of intrinsic activation, the quantity and quality of stimuli, as well as many physiological and/or pathological conditions can determine whether the response of polymorphonuclear leukocytes is more protective or destructive of the parodontium.

Bacteria↗
PubMed1986

Studies on thylakoid phosphorylation and noncyclic electron transport.

The effect of thylakoid phosphorylation on noncyclic electron transport in spinach chloroplasts was investigated by measuring both the reduction of nicotinamide adenine dinucleotide phosphate (NADP) and the steady-state redox level of the primary electron acceptor quinone of photosystem II (Q) during electron flow to NADP. These data are compared with the theoretical predictions for an electron transport model which relates both the redox levels of Q and the photosystem II optical cross section to the overall velocity of noncyclic electron flow. It is demonstrated that transfer of 15-20% of the photosystem II antenna to photosystem I may stimulate electron flow to NADP only if Q is less than 60-70% oxidized (this condition exists with our thylakoids, even at extremely low absorption fluxes, when the illumination is not specifically enriched in photosystem I absorbed wavelengths); in phosphorylated thylakoids the steady-state redox level Q is substantially shifted to a more oxidized one (measurements of this parameter using light of different wavelengths quantitatively support the idea that thylakoid phosphorylation leads to increased photosystem I and decreased photosystem II cross sections); thylakoid phosphorylation leads to stimulated noncyclic electron flow to NADP only when the increased photosystem I antenna is able to bring about large increases in the steady-state level of oxidized Q.

Chlorophyll↗
PubMed1982

Free-cortisol assay by immunoextraction: comparison with an equilibrium dialysis procedure.

We describe a new method for directly determining the apparent free cortisol concentration in plasma samples by use of an antibody-coated test-tube RIA. Buffer-diluted plasma or standard serum is added to antibody-coated test tubes, incubated at 4 degrees C for 4 h, and the solutions are aspirated. 125I-labeled cortisol is added to each tube and incubated for 3 h at 4 degrees C. Then the insides of the tubes are washed and their radioactivities counted. The standard curve is in terms of free cortisol, the standard serum solutions having been measured with an equilibrium dialysis procedure. Plasma samples (n = 155) from normal subjects and from various patients, measured with the new immunoextraction method and the equilibrium dialysis technique, gave results that correlated well (r = 0.847, p less than 0.001). Results by this direct RIA also correlate well with the clinical adrenocortical status of patients for whom data on total plasma cortisol may be misleading. This simple, easy RIA is suited to be the routine method for free cortisol in plasma.

Anorexia Nervosa↗
PubMedDate not supplied

Myocardial cell damage during attacks of vasospastic angina in the absence of persistent electrocardiographic changes.

We have investigated whether vasospastic anginal attacks might be associated with myocardial cell damage even when permanent ORS or ST-T changes are absent. We obtained serum time-activity curves of creatine kinase MB, of myoglobin, and of alpha hydroxybutyrate dehydrogenase in 15 patients with vasospastic angina admitted to our Coronary Care Unit (CCU). A slight but consistent rise and fall of both myoglobin and creatine kinase MB was observed in 7 patients (4 presented a definitive myocardial uptake of 99mTc pyrophosphate, and I had a faint deposition). A similar pattern was observed for myoglobin alone in 3 patients (1 presented a negative myocardial scan), while no consistent changes were found in the remaining 5 patients (2 presented a faint deposition of 99mTc pyrophosphate). No significant change of alpha hydroxybutyrate dehydrogenase was observed in any of the patients. The coherent rise and fall of the levels of myocardial cytosolic components after prolonged episodes of vasospastic angina suggests that cell damage may occur even in the absence of persistent QRS and ST-T changes.

Adult↗