Showing papers by "University of Turin published in 1981"

Photochemical cleavage of water by photocatalysis

Abstract: A bifunctional redox catalyst, composed of Pt and RuO2 co-deposited on a colloidal TiO2 carrier, is a highly potent mediator for water decomposition by visible light1. The system contains apart from the sensitizer (Ru(bipy)2+3) an electron relay—methylviologen. The latter is reduced on light excitation, and the photoreaction is coupled with catalytic steps2 generating H2 and O2 from water. To rationalize the surprisingly high efficiency of this photoredox system, we proposed a mechanism involving species adsorbed at the TiO2 surface. This led us to explore sensitizers which through suitable functionalization show an enhanced affinity for adsorption at the particle–water interface. We describe here the performance of electron relay-free systems capable of efficiently decomposing water into H2 and O2 under visible light illumination. A bifunctional redox catalyst composed of RuO2 and Pt co-supported on colloidal TiO2 particles is used. The only other component present is a sensitizer. Amphiphilic surfactant derivatives of Ru(bipy)2+3 exhibit extremely high activity in promoting the water cleavage process. Adsorption of the sensitizer at the TiO2 particle–water interface and electron ejection into the TiO2 conduction band are evoked to explain the observations. Exposure to UV radiation leads to efficient water cleavage in the absence of sensitizer.

Microdissection and cloning of DNA from a specific region of Drosophila melanogaster polytene chromosomes.

Abstract: Fragments from section 3 of the salivary gland X chromosome of D. melanogaster were dissected with a micromanipulator. The DNA was extracted, cut and ligated to a λ vector in a volume of a few nanoliters in an oil chamber monitored through a microscope. From about 10 pg of DNA we obtained 80 recombinant clones, a sample of which were analysed and shown to contain Drosophila DNA which hybridises in situ to the region of section 3 of the X chromosome. With this technique we can isolate clones from any desired region as small as 200 kb from the euchromatic arms of polytene chromosomes.

Release of platelet-activating factor (PAF) and histamine. II. The cellular origin of human PAF: monocytes, polymorphonuclear neutrophils and basophils.

Abstract: The origin of platelet activating factor (PAF) from human leucocytes was investigated. Purified monocytes release PAF passively at pH 10.6, when challenged with Ionophore A 23187 or under phagocytic stimuli. Pure preparations of polymorphonuclear neutrophils liberate PAF passively, when challenged with C5a, neutrophil cationic proteins (CP), their carboxypeptidase B derived products (C5a des Arg, CP des Arg) or under phagocytic stimuli. Basophil rich buffy coat cells release PAF when challenged with C5a, CP, anti-IgE (in low amount) or Synacthen concomitantly with basophil degranulation and histamine release. Electron microscopy studies, carried out on Synacthen-stimulated basophil rich buffy coat, provide morphological evidence for platelet-basophil interaction. In conclusion our data demonstrate that PAF can be released from different leucocyte populations. However, the stimuli able to trigger such release appear to have some specificity for the cell target.

Furoxans and Benzofuroxans

Abstract: Publisher Summary This chapter discusses the properties and preparation methods of furoxans and benzofuroxans. The history of its structure is briefly outlined. Many furoxan structures are determined by crystallographic methods, and as a result the dimensions of the heterocyclic ring are known in a wide variety of fused and substituted examples. Dynamic resonance effects (DNMR)—signal-broadening and coalescence phenomena at medium and fast exchange rates—are characteristic of furoxans fused to aromatic rings. The spectrum of benzotrifuroxan is analyzed and compared with that of the trifurazan. The methods of benzofuroxans preparation are: (1) dimerization of nitrile oxides, (2) dehydrogenataion of dioximes, (3) preparations from olefins and nitrogen oxides, (4) miscellaneous furoxan synthesis, and (5) benzofuroxans and other aromatic-ring-fused systems. The simple deoxygenation of furoxans to furazans is provided. Furoxans can be reduced in a variety of ways, depending upon the conditions used. It includes: (1) catalytic hydrogenation, (2) reduction with complex hydrides, (3) reduction with phosphorus compounds, (4) reduction with dissolving metals and metal ions, (5) electrochemical and other reducing methods. The chapter considers the principal substituent groups on the furoxan ring and the reactions they undergo.

Idiopathic Myelofibrosis: a Possible Role for Immune‐Complexes in the Pathogenesis of Bone Marrow Fibrosis

Abstract: Sixteen patients with idiopathic myelofibrosis (IM) have been investigated with respect to the possibility that immune mechanisms may be of importance in the pathogenesis of bone marrow fibrosis. The following points appear relevant: (1) immune-complexes (IC) are detectable with different techniques in a high percentage of patients with IM. Their presence is associated with evidence of bone-marrow histological markers of immune activity. (2) IgG is the main Ig class in the composition of IM IC. The results obtained favour the hypothesis that autoimmune mechanisms are involved in IM patients.

Origin of a thick, redeposited carbonate bed in Eocene turbidites of the Hecho Group, south-central Pyrenees, Spain

Abstract: Large-scale carbonate beds interbedded in basin-plain turbidites of the Eocene Hecho Group, northern Spain, are interpreted as giant turbidity-current deposits because of their internal organization and lateral extent. One such bed, the Roncal Unit, has been traced down the axis of the basin for 75 km and commonly reaches thicknesses in excess of 100 m. Internally, the Roncal Unit displays an overall upward decrease in grain size, from a basal megabreccia with large slabs of carbonate platform debris to a calcareous mudstone. The Roncal Unit was probably deposited from a highly mobile and competent sediment gravity flow generated by an earthquake shock, which led to the catastrophic collapse and subsequent transport of the upper part of a carbonate platform flanking the basin.

Enthalpies of solvation in cyclohexane and in water for homologous aliphatic ketones and esters

Abstract: The standard enthalpies of solution at infinite dilution were determined for homologous aliphatic ketones and esters in water and in cyclohexane, using a rotating Calvet calorimeter, and solution concentrations about 5×10−4 mole fraction. Vaporization enthalpies, obtained for each compound with an effusion calorimetric cell, were added to calculate the solvation enthalpies. Their dependence on the number of carbon atoms in the chain is discussed in terms of the Friedman and Krishnan treatment. The effect of polarization of the functional groups is evaluated, and separation from the influence of chain length and the hydrophobic interactions of the methylenes is attempted. For the aqueous solutions, the rearrangement in the structure of the solvent around solute molecules is also considered in relation to deviations from linearity. Comparisons are made with solvation enthalpies obtained for ketones and esters with branched or cyclic substitutes.

Insulin resistance in the aged: the role of the peripheral insulin receptors.

Abstract: In the healthy subject, glocose tolerance tends to decrease with age due to impaired insulin secretion and/or decreased peripheral insulin activity. An oral glucose (100 g) tolerance test was performed on 12 aged (70 ± 4 yr) and 8 young (32 ± 7 yr) subjects; these subjects underwent laparatomy for cholecystectomy or the management of abdominal diseases. Subcutaneous adipose tissue was removed during surgery and fat cells, prepared according to a personal modification of Rodbell's method, were incubated in a medium containing monoiodo- and cold insulin to evaluate insulin binding and affinity constants. The results of the tolerance test pointed to an insulin resistant state i.e., impaired glucose tolerance coupled with normal plasma insulin, as previously shown also by us using other methods in the aged subject. The binding study demonstrates a distinct insulin receptor decrease in fat cells from the older subjects (185,000 ± 19,200 as opposed to 310,000 ± 12,000), without any change in affinity constants. The result indicates that insulin resistance in the aged may be attributed at least in part to a reduction in the number of insulin receptors on the target cells. This could be a consequence of aging itself, as proposed by other workers in the case of old fat rats.

Rates of synthesis and degradation of ribosomal ribonucleic acid during differentiation of Dictyostelium discoideum.

Abstract: Synthesis of ribosomes and ribosomal ribonucleic acid (RNA) continued during differentiation of Dictyostelium discoideum concurrently with extensive turnover of ribosomes synthesized during both growth and developmental stages. We show here that the rate of synthesis of 26S and 17S ribosomal RNA during differentiation was less than 15% of that in growing cells, and by the time of sorocarp formation only about 25% of the cellular ribosomes had been synthesized during differentiation. Ribosomes synthesized during growth and differentiation were utilized in messenger RNA translation to the same extent; about 50% of each class were on polyribosomes. Ribosome degradation is apparently an all-or-nothing process, since virtually all 80S monosomes present in developing cells could be incorporated into polysomes when growth conditions were restored. By several criteria, ribosomes synthesized during growth and differentiation were functionally indistinguishable. Our data, together with previously published information on changes in the messenger RNA population during differentiation, indicate that synthesis of new ribosomes is not necessary for translation of developmentally regulated messenger RNA. We also establish that the overall rate of messenger RNA synthesis during differentiation is less than 15% of that in growing cells.

Ultrastructural aspects of endomycorrhizas in the ericaceae ii.

Abstract: Summary The endomycorrhizal infection in Vaccinium myrtillus is limited to the cortical cells of the fine hair roots; the fungi responsible have simple septa with associated Woronin bodies (Ascomycetes). Hyphae penetrating into cells are surrounded by a layer of inner host wall material which diminishes with intracellular development of the fungus. In living cells hyphae are separated from host cytoplasm by continuous host plasmalemma and there is no evidence of their lysis or digestion by the plant cell. This biotrophic relationship (living host cell and fungus) appears to predominate in late summer and autumn when new root formation and mycorrhizal infection are most important. During other periods of the year living or dead fungus in moribund host cells seem to be the most common situation.

Exact–exchange Hartree–Fock calculations for periodic systems

Abstract: An all-electron ab initio Hartree–Fock calculation (in the impulse approximation) of the Compton profiles of aluminium in the [100], [110] and [111] directions is presented. Comparison is made with previous experimental and calculated results; in spite of the fact that a minimal basis set is employed, the agreement with measured Compton profiles is good, and within the limits of the experimental uncertainty.

Idiotypic lymphocytes in human monoclonal gammopathies.

Abstract: We have studied seven human monoclonal gammopathies using anti-idiotypic sera. In benign and malignant gammopathies, we have observed a similar number of B lymphocytes bearing idiotypic specificities also found on the monoclonal protein. These observations suggest that the plasma cell population is only a phenotypic expression of a tumoral event occurring in a B lymphocytic precursor which can still completely differentiate. In four myeloma patients and one benign monoclonal gammopathy, we also observed T lymphocytes bearing receptors idiotypically cross-reactive with the monoclonal protein. The values ranged from 1.8 to 8.0 % within the purified T-cell population. In a first hypothesis, these T lymphocytes can belong to the tumoral clone itself. The tumoral event must occur at the level of a common precursor not yet determined to B or T pathway of differentiation. In a second hypothesis, these T lymphocytes are not cancerous but are induced by a strong perturbation of the idiotypic network, due to the enormous amount of the idiotypic B-cell tumoral subset.

Radio- and chemotherapy of malignant gliomas. Pathological changes in the normal nervous tissue.

Abstract: The pathological effects of radio- and chemotherapy on the normal nervous tissue have been studied in 42 brains with malignant gliomas. The brains have been examined by means of the complete study technique. In seven cases the picture of delayed radionecrosis has been found. Apart from this, many histological features have been related to post-operative survival, radiation dose, interval between radiation and death, chemotherapy, steroids, size and activity of the tumour. Some alterations, such as peritumoural necroses, macrophage areas, vessel wall degenerations etc. result from radiotherapy. The relations and pathogenesis are discussed.

Skin lesions in angioimmunoblastic lymphadenopathy: histological and immunological studies.

Abstract: Angioimmunoblastic lymphadenopathy with drysproteinaemia is reported (AILD) in four patients with different skin pictures. As the disease progresses two main forms predominate; papulonodular and erythroderma. In all cases the histological picture of the skin mirrors that of the lymph-node. Our results point to an increase in the peripheral blood, lymph-nodes and skin of T and subsequently of B lymphocytes suggesting that a proliferation of helper T cells and hence activation of the B-cell subpopulation may be involved in the pathogenesis of some cases of AILD.

Acute neurologic complications of hemodialysis. Study of 14,000 hemodialyses in 103 patients with chronic renal failure.

Abstract: We have examined and subjected to statistical analysis the transient acute neurological complications arising in the course of hemodialysis in 103 patients with chronic renal failure (13,969 hemodialysis sessions).

Myoepithelial cells in lobular carcinoma in situ of the breast: a parallel immunocytochemical and ultrastructural study.

Abstract: The distribution and morphology of myoepithelial cells in one case of normal breast and in 4 cases of lobular carcinoma in situ (LCIS) were studied by immunoperoxidase and immunofluorescence with antiactin antisera and by electron microscopy. The actinrich cells appeared to lay flattened on the basement membrane, or perpendicular to it, or appeared dislodged toward the center of the neoplastic ductules in the different cases.It is proposed that the presence of actin-rich cells inside the neoplastic aggregates represents a process of colonization of lobular carcinoma by myoepithelial cells dislodged from the basement membrane; a differentiation of some neoplastic cells toward myoepithelial elements might also be taken into consideration. The features here described could identify a preinvasive stage of LCIS.

Synthesis, Surface Activity and Micelle Formation of Novel Cyanine Dyes

Abstract: The synthesis, surface activity and micelle formation of three novel cyanine dyes with amphiphilic character is described. It is illustrated by combined surface tension and absorption measurements that in one case self-assembly is highly cooperative leading to aggregates with unique absorption properties.