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Biomedical subjects

L Andreotti

Publications and source records attributed to L Andreotti.

At least 19 recordsLinked to original sources
PubMed2001

Photoinitiated catalysis in Nafion membranes containing palladium(II) meso-tetrakis(N-methyl-4-pyridyl)porphyrin and iron(III) meso-tetrakis-(2,6-dichlorophenyl)porphyrin for O2-mediated oxidations of alkenes.

Immobilisation of both palladium(II) meso-tetrakis(N-methyl-4-pyridyl)porphyrin (PdTMPyP4+) and iron(III) meso-tetrakis(2,6-dichlorophenyl)porphyrin (FeTDCPP+) in the same membrane of Nafion creates a new composite system, in which the photoexcited palladium complex induces the O2-mediated oxidation of cyclohexene to the corresponding allylic hydroperoxide and the iron porphyrin works as a catalyst for specific oxygenations of cyclohexene and cyclooctene. The role of PdTMPyP4+ is to induce the photoactivation of O2 with visible light (lambda > 500 nm) to generate singlet oxygen (1O2) by means of energy transfer from the excited triplet state. Consequently, the 1O2-mediated oxidation of cyclohexene to cyclohexenyl hydroperoxide can be realised with a selectivity greater than 90%. Spectroscopic and photophysical investigations show that the tetracationic palladium porphyrin is mainly fixed to the external part of the Nafion membrane, it is characterised by a triplet-state lifetime significantly higher than that in the solution phase. The monocationic FeTDCPP+ is able to diffuse into the anionic cavities of Nafion, where it works as a catalyst for O2-mediated autooxidation processes that are initiated by the photogenerated hydroperoxides. These processes continue in the dark for many hours giving cyclohex-2-en-1-ol and trans-cyclohexane-1,2-diol monoethyl ether as main oxidation products. The presence of this ether, indirectly, reveals the formation of cyclohexene epoxide which undergoes a nucleophilic attack by ethanol and epoxide opening because of the strong acidic environment inside Nafion. The good photocatalytic efficiency of the oxidation process is demonstrated by an overall quantum yield of 1.1, as well as by a turnover value of 4.7 x 10(3) with respect to the iron porphyrin. When cyclooctene is present as co-substrate, it also undergoes oxygenation. In contrast to what was observed for cyclohexene, cyclooctene epoxide can be accumulated in a significant amount. As far as the stability of the system is concerned, FeTDCPP+ undergoes about 1% degradation during the process, while the Nafion matrix can be utilised several times without observable modification.

Alkenes↗
PubMed1999

Photochemically driven models of oxygenases based on the use of iron porphyrins.

Photoexcited iron porphyrins can be used to mimic the catalytic activity of cytochrome P-450 oxygenases both in the reduction of halogenated alkanes and in the oxidation of hydrocarbons by O2 itself at room temperature and atmospheric pressure. The results reported indicate that there is a similarity and a complementarity of photonic activation with other more conventional methods of activation of model systems of oxygenases. In fact, by irradiating at suitable wavelengths, it is possible to induce redox reactions which mimic those of natural oxygenases, avoiding the difficulties caused by parallel processes which could be expected when chemical reagents are used. These processes occur with good turnover values of the photocatalyst and in mild temperature and pressure conditions. By controlling the reaction environment, it is possible to address the selectivity of the process. In this regard, the very recent results obtained after heterogenization of the photocatalysts inside membranes of Nafion are particularly promising for the development of new biomimetic photocatalysts in heterogeneous or organized systems.

Animals↗
PubMed1990

Inspiratory muscle strength and respiratory drive in patients with rheumatoid arthritis.

In 15 patients with rheumatoid arthritis (RA) and in 12 age- and sex-matched normal subjects, we evaluated inspiratory muscle strength and respiratory control system. Inspiratory muscle strength was assessed by measuring maximal inspiratory pressure (MIP). Respiratory drive was assessed by evaluating surface electromyographic activity of the diaphragm (EMGd) during both room-air breathing and hypercapnic rebreathing. Compared to the predicted value (mean +/- 1.65 SD), MIP was significantly reduced in nine patients (60%). All told, we noticed a significant inverse relationship in the patients between MIP and duration of steroid therapy (p less than 0.01). During room-air breathing, both EMGd and mouth occlusion pressure (P0.1), expressed both in actual values and as percentage of MIP, were significantly greater in patients than in the normal control group (p less than 0.001 for both). Both EMGd and P0.1 (%MIP) response slopes to CO2 were significantly greater in patients than in the normal control group (p less than 0.01 and p less than 0.001, respectively) and significantly related to the functional stage of disease. During quiet breathing and for a PETCO2 of 60 mm Hg, both EMGd (p less than 0.01 and p less than 0.05, respectively) and P0.1 (%MIP) (p less than 0.01 and p = 0.001, respectively) were inversely related to MIP. These results indicate that RA patients may exhibit inspiratory muscle weakness and increased respiratory drive. Steroid myopathy and rheumatoid myositis could explain the reduction in MIP, whereas neural afferents arising from respiratory muscle, lung, or joint receptors could be involved in the observed increase in neural drive.

Arthritis, Rheumatoid↗
PubMed1988

Chick heart peptidergic innervation: localization and development.

Localization and development of chick heart peptidergic innervation (Substance P, VIP and Somatostatin) were investigated by means of immunofluorescence technique. The peptidergic component of the heart innervation was observed, for the first time, in older than 11 day chick embryos, i.e., subsequently to the appearance of the cholinergic component. The peptidergic structures achieve nearly full development in about 16-17 day embryos. Substance P is the most represented of the three peptides. It is localized both in nerve bundle fibers and in isolated fibers within the myocardium, the pericardium, the vessel walls; it is also present in fibers of some heart base ganglia. VIP is mostly contained in some thick single fibers travelling along the vessel walls of the heart base, the myocardium and the pericardium. Some VIP immunoreactive cells were also observed in the base ganglia. Somatostatin is mostly contained in some ganglia cells, whilst thin Somatostatin-immunoreactive fibers form a rich plexus among the atrial and ventricular myofibers, without contacting the vessel walls.

Animals↗
PubMed1986

Aortic connective tissue in atherosclerotic aorta--a biochemical study.

Biochemical analysis of the extracellular matrix of human aortas was performed on samples of ascending and descending aortas affected by atherosclerosis in comparison with a control group of nonatherosclerotic aortas. Ulcerated or heavily calcified atheromas were excised and excluded from the analysis in order to differentiate biochemical alterations leading to the formation of atheromas from those due to complications of already formed atheromas. Our results show that the development of atheromas brings about an extensive destruction of elastic fibers and muscular cells, and their place is occupied by other components of the extracellular matrix, most notably, collagen, non-uronic sugars, water, and lipids, which were found significantly increased.

Adult↗
PubMed1985

Biochemical analysis of dermal connective tissue in subjects affected by primary uncomplicated varicose veins.

Biochemical analysis of dermal connective tissue was carried out in 14 subjects affected by primary uncomplicated varicose veins and 14 controls. Skin samples were taken, according to fixed criteria, from operation pieces of total mastectomy for breast cancer. The results suggest that the dermal tissue in these subjects is just thinner than that of controls, confirming previous similar clinical findings. The elective reduction of the collagen content observed, unassociated with changes of other components of the dermal connective tissue, brings evidence for a systemic biochemical defect of the extracellular matrix i.e. a collagen defect affecting the entire body structure and not only the varicose or pre-varicose veins of the lower limbs.

Adult↗
PubMed1985

Aortic connective tissue in ageing--a biochemical study.

The biochemical analysis of samples of aortic connective tissue was carried out in 22 subjects from 9 to 84 years old. Aortic samples were taken at necropsy performed after sudden or, more often, traumatic death. The results suggest that aging of the aorta is accompanied by an increase both in collagen content and in total sugar content when expressed as mg/cm2 while the elastin content, when expressed in the same way, does not undergo any variation.

Adolescent↗
PubMed1983

Connective tissue in aging lung.

Collagen, elastin and structural glycoproteins were measured in 21 intact lungs taken at postmortem examination after sudden death from subjects aged from 15 to 83. The data were expressed as milligrams per cubic centimeter of lung peripheral parenchyma inflated and fixed at the standard pressure of 25 cm H2O to exclude the pitfall of referring to dried tissue weight. The volume/weight ratio of inflated dried lung parenchyma increased significantly with aging; likewise the collagen content decreased and so did the collagen/elastin ratio, while the elastin content did not show any significant correlation with age. The present findings indicate that biochemical, morphological and functional data on the senile lung agree well.

Adolescent↗
PubMed1980

[Incidence of the manifestations of the so-called status varicosus of Curtius in subjects with idiopathic varices of the lower extremities].

Two groups of subjects have been studied: the first one affected by varicose veins in lower legs, the second one as control (both groups include 138 subjects, mostly corresponding about age, sex and general health conditions). Acrocyanosis, blue sclerae, juvenile spontaneous epistaxis, hand's primary osteoarthrosis, articular hypermobility, thin skin and hernia were present more frequently in the group affected by varicose veins, the difference being statistically very significant. We suggest that mechanical revealing factors lead to the development of varicose veins in subjects who have a constitutional and probably hereditary systemic weakness of connective tissue network.

Adult↗
PubMed1979

Connective tissue in varicose veins.

The collagen, elastin, total sugar, and nonscleroprotein content was evaluated in 32 samples of saphenous varicose vein and in 34 controls. A significantly lower collagen and elastin content was found in the varicose samples without correlation with the degree of pathologic broadening. Otherwise the total sugars and the soluble nonscleroproteins were found to be increased in varicose samples. The results are more significant when expressed as milligrams per surface unit of endothelium. Our data support the hypothesis that the decrease in collagen and elastin content is a primary rather than secondary change.

Carbohydrates↗