Showing papers by "University of Milan published in 1992"

The complete DNA sequence of yeast chromosome III.

Abstract: The entire DNA sequence of chromosome III of the yeast Saccharomyces cerevisiae has been determined. This is the first complete sequence analysis of an entire chromosome from any organism. The 315-kilobase sequence reveals 182 open reading frames for proteins longer than 100 amino acids, of which 37 correspond to known genes and 29 more show some similarity to sequences in databases. Of 55 new open reading frames analysed by gene disruption, three are essential genes; of 42 non-essential genes that were tested, 14 show some discernible effect on phenotype and the remaining 28 have no overt function.

Genetic evidence for a novel familial Alzheimer's disease locus on chromosome 14

Abstract: Familial Alzheimer's disease (FAD) has been shown to be genetically heterogeneous, with a very small proportion of early onset pedigrees being associated with mutations in the amyloid precursor protein (APP) gene on chromosome 21, and some late onset pedigrees showing associations with markers on chromosome 19. We now provide evidence for a major early onset FAD locus on the long arm of chromosome 14 near the markers D14S43 and D14S53 (multipoint lod score z = 23.4) and suggest that the inheritance of FAD may be more complex than had initially been suspected.

SRY, like HMG1, recognizes sharp angles in DNA.

Abstract: HMG boxes are DNA binding domains present in chromatin proteins, general transcription factors for nucleolar and mitochondrial RNA polymerases, and gene- and tissue-specific transcriptional regulators. The HMG boxes of HMG1, an abundant component of chromatin, interact specifically with four-way junctions, DNA structures that are cross-shaped and contain angles of approximately 60 and 120 degrees between their arms. We show here also that the HMG box of SRY, the protein that determines the expression of male-specific genes in humans, recognizes four-way junction DNAs irrespective of their sequence. In addition, when SRY binds to linear duplex DNA containing its specific target AACAAAG, it produces a sharp bend. Therefore, the interaction between HMG boxes and DNA appears to be predominantly structure-specific. The production of the recognition of a kink in DNA can serve several distinct functions, such as the repair of DNA lesions, the folding of DNA segments with bound transcriptional factors into productive complexes or the wrapping of DNA in chromatin.

Expression of the potent inflammatory cytokines, granulocyte-macrophage-colony-stimulating factor and interleukin-6 and interleukin-8, in bronchial epithelial cells of patients with asthma

Abstract: We have previously demonstrated that cultured human bronchial epithelial cells produce cytokines with potent proinflammatory properties on exposure to several stimuli in vitro, and we have hypothesized that these epithelial cell-derived factors may contribute to the pathogenesis of some inflammatory diseases of the bronchial mucosa, particularly asthma, by promoting the infiltration of granulocytes and T cells and their local activation. We provide, in this study, direct evidence of an increased expression of granulocyte-macrophage-colony-stimulating factor, interleukin-6, and interleukin-8 genes and proteins in bronchial epithelium from patients with symptomatic asthma. The up regulation of the production of these cytokines in bronchial epithelial cells of patients with asthma could be abolished in vitro by corticosteroids (hydrocortisone, 10 −7 mol/L), but the up regulation also spontaneously disappeared during a period of 6 days after the removal of the cells from the diseased tissue.

Importance of gravitational spreading in the tectonic and volcanic evolution of Mount Etna

Abstract: THE interaction between gravity and thermal effects largely determines the structural and magmatic evolution of volcanic constructs at scales spanning several orders of magnitude, from small cones to the oceanic crust1–3. Although gravitational spreading is a direct consequence of this interaction and a fundamental process in volcano growth, it is rarely recognized as such. Here we describe a striking example of this process, at Etna volcano, in Italy. The volcano and its clay-rich substratum are slowly spreading towards the east and south, driven by gravity. Spreading produces extensional structures in the summit region and contpressional structures at the base of the volcano. Eastward movement of the volcanic edifice over a stationary magma supply may be the cause of an apparent westward migration of volcanic activity. As gravitational spreading seems to control the location and magnitude of shallow seismicity and flank eruptions, an appreciation of its effects could become an essential element of future volcanic hazard evaluation. Our model proposed here for Etna may also be relevant to a reinterpretation of the geological history of a number of other volcanoes.

Exo-endocytotic recycling of synaptic vesicles in developing processes of cultured hippocampal neurons.

Abstract: In mature neurons synaptic vesicles (SVs) undergo cycles of exo-endocytosis at synapses. It is currently unknown whether SV exocytosis and recycling occurs also in developing axons prior to synapse formation. To address this question, we have developed an immunocytochemical assay to reveal SV exo-endocytosis in hippocampal neurons developing in culture. In this assay antibodies directed against the lumenal domain of synaptotagmin I (Syt I), an intrinsic membrane protein of SVs, are used to reveal exposure of SV membranes at the cell surface. Addition of antibodies to the culture medium of living neurons for 1 hr at 37 degrees C resulted in their rapid and specific internalization by all neuronal processes and, particularly, by axons. Double immunofluorescence and electron microscopy immunocytochemistry indicated that the antibodies were retained within SVs in cell processes and underwent cycles of exo-endocytosis in parallel with SV membranes. In contrast, another endocytotic marker, wheat germ agglutinin, was rapidly cleared from the processes and transported to the cell body. Antibody-labeled SVs were still present in axons several days after antibody loading and became clustered at presynaptic sites in parallel with synaptogenesis. These results demonstrate that SVs undergo multiple cycles of exo-endocytosis in developing neuronal processes irrespective of the presence of synaptic contacts.

Prevention of First Bleeding in Cirrhosis: A Meta-Analysis of Randomized Trials of Nonsurgical Treatment

Abstract: OBJECTIVE To assess the effectiveness of beta-blockers and endoscopic sclerotherapy in the prevention of first bleeding and reduction of mortality in patients with cirrhosis and esophagogastric varices. DATA SOURCES Pertinent studies were selected using MEDLINE (1980 to 1990), reference lists from published articles or reviews, and congress abstract lists. STUDY SELECTION Randomized trials comparing beta-blockers or sclerotherapy with a nonactive treatment. Nine randomized clinical trials of beta-blockers and 19 trials of sclerotherapy were reviewed. Seven trials of beta-blockers and 15 of sclerotherapy were published as full papers. DATA EXTRACTION Crude rates of bleeding and death in treated and control groups were extracted from each trial by three independent observers according to the intention-to-treat principle. The quality of published papers was systematically assessed and scored. DATA SYNTHESIS The Mantel-Haenszel-Peto method was used for statistical evaluation of heterogeneity and for pooling of the results. No substantial heterogeneity was found, and the incidence of bleeding in trials of beta-blockers was significantly reduced (pooled odds ratio, 0.54; 95% CI, 0.39 to 0.74), particularly in patients with large or medium-sized varices or in those with varices and a hepatic vein pressure gradient above 12 mm Hg; however, only a trend toward reduced mortality was obtained. Sclerotherapy trials were highly heterogeneous in the direction of the treatment effects on both bleeding (pooled odds ratio, 0.6; CI, 0.49 to 0.74) and mortality (pooled odds ratio, 0.76; CI, 0.61 to 0.94). The quality of the trials and the rate of bleeding in the untreated groups were the major sources of heterogeneity. The favorable results of sclerotherapy were obtained in trials with high bleeding rates among controls; several of these trials had a low quality score. CONCLUSIONS Beta-blockers may be recommended for prevention of first bleeding in cirrhotic patients with varices who have a high risk for bleeding. The effectiveness of sclerotherapy remains undetermined. Further trials in high-risk patients may prove useful if improved criteria to predict bleeding risk become available.

Persistent blood pressure increase induced by heavy smoking.

Abstract: Objective: To test the hypothesis that heavy smoking is associated with a persistent increase in blood pressureDesign: In 10 normotensive smokers asked to smoke one cigarette every 15 min for 1 h, blood pressure and heart rate were continuously monitored during the smoking period and during the prec

Treatment of Advanced Squamous-Cell Carcinoma of the Head and Neck with Alternating Chemotherapy and Radiotherapy

Abstract: Background. For patients with advanced, unresectable squamous-cell carcinoma of the head and neck, radiotherapy is the standard treatment but has poor results. We therefore designed a randomized trial to determine whether alternating chemotherapy with radiotherapy would improve the survival of such patients. Methods. Patients in the trial had biopsy-confirmed unresectable, previously untreated Stage III or IV, squamous-cell carcinoma of the oral cavity, pharynx, or larynx. They were randomly assigned to chemotherapy consisting of four cycles of intravenous cisplatin (20 mg per square meter of body-surface area per day for five consecutive days) and fluorouracil (200 mg per square meter per day for five consecutive days) alternating with radiotherapy in three two-week courses (20 Gy per course; 2 Gy per day, five days per week), or to radiotherapy alone (up to 70 Gy; 2 Gy per day, five days per week). Results. The 80 patients given chemotherapy alternating with radiotherapy and the 77 given radiot...

Synaptic vesicle-associated Ca2+/calmodulin-dependent protein kinase II is a binding protein for synapsin I.

Abstract: Synapsin I is a synaptic vesicle-associated phosphoprotein that is involved in the modulation of neurotransmitter release. Ca2+/calmodulin-dependent protein kinase II, which phosphorylates two sites in the carboxy-terminal region of synapsin I, causes synapsin I to dissociate from synaptic vesicles and increases neurotransmitter release. Conversely, the dephosphorylated form of synapsin I, but not the form phosphorylated by Ca2+/calmodulin-dependent protein kinase II, inhibits neurotransmitter release. The amino-terminal region of synapsin I interacts with membrane phospholipids, whereas the C-terminal region binds to a protein component of synaptic vesicles. Here we demonstrate that the binding of the C-terminal region of synapsin I involves the regulatory domain of a synaptic vesicle-associated form of Ca2+/calmodulin-dependent protein kinase II. Our results indicate that this form of the kinase functions both as a binding protein for synapsin I, and as an enzyme that phosphorylates synapsin I and promotes its dissociation from the vesicles.

Evidence of H- and L-chains have co-operative roles in the iron-uptake mechanism of human ferritin.

Abstract: The ability to incorporate iron in vitro was studied in homopolymers of human ferritin L-chain, human ferritin H-chain and its variants and in homopolymer mixtures. The H-chain variants carried amino acid substitutions in the ferroxidase centre and/or in carboxy residues on the cavity surface. Iron incorporation was examined by gel electrophoresis of the reaction products by staining for iron and protein. It was found that inactivation of the ferroxidase centre combined with the substitution of four carboxy groups on the cavity abolished the ability of H-chain ferritin to incorporate iron. Competition experiments with limited amounts of iron showed that, at neutral pH, L-chain ferritin is more efficient in forming iron cores than the H-chain variants altered at the ferroxidase activity or in the cavity. Competition experiments at pH 5.5 demonstrated that L-chain apoferritin is able to incorporate iron only when in the presence of H-chain variants with ferroxidase activity. The results indicate that L-chain apoferritin has a higher capacity than the H-chain apoferritin to induce iron-core nucleation, whereas H-chain ferritin is superior in promoting Fe(II) oxidation. The finding of cooperative roles of the H- and L-chains in ferritin iron uptake provides a clue to understanding the biological function of isoferritins.

Spinodal-type dynamics in fractal aggregation of colloidal clusters.

Abstract: The aggregation of dense colloidal solutions has been investigated by means of low-angle static light scattering. We show that the scattered pattern exhibits a finite-q-vector peak, whose intensity and position ${\mathit{q}}_{\mathit{m}}$ change with time. We find that the intensity distributions scale according to S(q/${\mathit{q}}_{\mathit{m}}$,t)=${\mathit{q}}_{\mathit{m}}$(t${)}^{\mathrm{\ensuremath{-}}\mathit{d}}$F(q/${\mathit{q}}_{\mathit{m}}$), in agreement with the scaling law for spinodal decomposition. While d=3 for spinodal decomposition, here scaling requires that d=${\mathit{d}}_{\mathit{f}}$, the fractal dimension of the clusters.

Jawbone enlargement using immediate implant placement associated with a split-crest technique and guided tissue regeneration.

Abstract: Five patients with sufficient vertical bone height but insufficient bone width for implant placement were chosen for treatment with a split-crest technique combined with guided tissue regeneration. The surgical technique involved splitting the alveolar ridge longitudinally in two parts, provoking a greenstick fracture. A chisel was then used to make a fine cut and spread apart the two cortical plates. Implants were then placed. Implants and defects were covered with expanded polytetrafluoroethylene membranes. Biometrical examination showed a gain in bone width, varying between 1 and 4 mm; maxillary sites showed greater ridge enlargement. Histologic examination showed regeneration of bone tissue between the two portions of the split crest. This membrane technique could be effective and predictable for horizontal ridge augmentation associated with immediate implant placement.

Videoendoscopic pulmonary lobectomy for cancer.

Abstract: A videothoracoscopic right lower pulmonary lobectomy is reported. The excision was done in a 71-year-old man suffering from an adenocarcinoma of the right lower lobe, with an apparent absence of lymphnodal and systemic metastasis. The procedure has been performed using four 10-mm cannulas and a minimal inframammary thoracotomy (4 cm) by inserting a chip camera linked to the thoracoscope and connected to external monitors. The lobar hilar structures were dissected and then sutured-divided with Endo-GIA R shots. The specimen was extracted through the minimal thoracotomy. The postoperative course was uneventful with minimal postoperative pain, and the patient was discharged after complete surgical recovery with excellent functional and cosmetic results. This procedure in selected patients is a new and promising possibility in chest videoendoscopic surgery.

Cloning by functional complementation of a mouse cDNA encoding a homologue of CDC25, a Saccharomyces cerevisiae RAS activator.

Abstract: In the yeast Saccharomyces cerevisiae genetic and biochemical evidence indicates that the product of the CDC25 gene activates the RAS/adenylyl cyclase/protein kinase A pathway by acting as a guanine nucleotide protein. Here we report the isolation of a mouse brain cDNA homologous to CDC25. The mouse cDNA, called CDC25Mm, complements specifically point mutations and deletion/disruptions of the CDC25 gene. In addition, it restores the cAMP levels and CDC25-dependent glucose-induced cAMP signalling in a yeast strain bearing a disruption of the CDC25 gene. The CDC25Mm-encoded protein is 34% identical with the catalytic carboxy terminal part of the CDC25 protein and shares significant homology with other proteins belonging to the same family. The protein encoded by CDC25Mm, prepared as a glutathione S-transferase fusion in Escherichia coli cells, activates adenylyl cyclase in yeast membranes in a RAS2-dependent manner. Northern blot analysis of mouse brain poly(A)+ RNA reveals two major transcripts of approximately 1700 and 5200 nucleotides. Transcripts were found also in mouse heart and at a lower level in liver and spleen.

Increased right caudate nucleus size in obsessive-compulsive disorder: Detection with magnetic resonance imaging

Abstract: Magnetic resonance images were used to measure the volume of the head of the caudate nucleus in 20 patients with obsessive-compulsive disorder and 16 normal control subjects. The obsessive-compulsive patients showed a significant increase in the volume of the right side of the head of the caudate nucleus compared with that of control subjects. This finding was not correlated with demographic, psychopathological, or clinical characteristics.

Isolation of endophytic streptomyces strains from surface-sterilized roots.

Abstract: When the roots of 28 plant species were surface sterilized and incubated on agar medium, endophytic actinomycetes in the root cortex were observed by direct microscopic observation and pure culture techniques

The Valanginian carbon isotope event: a first episode of greenhouse climate conditions during the Cretaceous

Abstract: Lower Cretaceous pelagic carbonates outcropping along the Southern Alps of northern Italy provide a record of Tethyan palaeoceanography as well as of low frequency fluctuations in the global carbon cycle. The carbonate C-isotope stratigraphy established at five selected localities in the Southern Alps allows an accurate picture to be drawn of the duration and amplitude of the Valanginian C-isotope event. δ13C values near 1.25–1.50% determined in Berriasian and lower Valanginian sediments are replaced by more pdsitive δ13C values near 3% in the late Valanginian. The carbonate C-isotope excursion ends in the early Hauterivian with values fluctuating between 1.5% and 2%. The carbonate C-isotope excursion is accompanied by a positive excursion in the total organic carbon C-isotope curve. The Valanginian C-isotope excursion identified in Tethyan sediments correlates with a C-isotope excursion recorded in the western North Atlantic, in the Gulf of Mexico, and in the Central Pacific (DSDP Sites 534,391,535 and 167). By analogy with the Aptian stage, also marked by a significant positive C-isotope excursion, the time of positive δ13C values is regarded as a time of accelerated carbon cycling coupled with increased burial rates of organic carbon and detrital material in oceanic sediments. A warm and humid climate, possiblycoupled with a high atmospheric CO2 content and a high global sea-level, may have triggered the acceleration of the global carbon cycling. In this case the Valanginian C-isotope event would reflect a first episode of Greenhouse Earth conditions during the Cretaceous.

Molecular orbital cluster model study of bonding and vibrations of CO adsorbed on MgO surface

Abstract: The interaction of CO with the MgO(100) surface has been investigated by means of all electron cluster model calculations. The CO molecule is bound on the Mg2+ site of MgO with a chemisorption energy of about 0.2 eV. The binding mechanism is electrostatic in nature and arises almost entirely from the interaction of the weak electric field generated by the ionic surface and the CO charge distribution, with negligible contributions from chemical effects as the CO σ donation. When CO is bound through carbon, its vibrational frequency increases with respect to the gas-phase value. This shift, Δ, has been analyzed and decomposed into the sum of different contributions. It is found that the positive Δω does not arise entirely from the field–dipole interaction but is due, in part, to the increase in Pauli repulsion occurring when the CO molecule vibrates in the presence of the surface “wall.” A stronger electrostatic interaction, bringing the CO adsorbate closer to the surface, increases this wall effect and results in a more pronounced positive ω shift. It is also found that the two CO orientations exhibit opposite shifts in ωe, thus, the two orientations can be distinguished, in principle, by IR spectroscopy. The analysis of our ab initio cluster wave functions gives a very different picture than the standard view of the metal–CO bond as arising from σ donation and π back donation.