Showing papers by "University of Florence published in 1990"

The construction of the L3 experiment

Abstract: The L3 experiment is one of the six large detectors designed for the new generation of electron-positron accelerators. It is the only detector that concentrates its efforts on limited goals of measuring electrons, muons and photons. By not attempting to identify hadrons, L3 has been able to provide an order of magnitude better resolution for electrons, muons and photons. Vertices and hadron jets are also studied. The construction of L3 has involved much state of the art technology in new principles of vertex detection and in new crystals for large scale electromagnetic shower detection and ultraprecise muon detection. This paper presents a summary of the construction of L3.

Excitatory amino acid release and free radical formation may cooperate in the genesis of ischemia-induced neuronal damage

Abstract: Excessive stimulation of excitatory amino acid (EAA) receptors and abnormal production of oxygen-derived free radicals have repeatedly been implicated in the series of events linking brain hypoxia or ischemia to neuronal death. We report here that in rat hippocampal slices the KCl-stimulated output of labeled D-3H aspartate or of endogenous aspartate and glutamate significantly increased under in vitro simulated hypoxic, hypoglycemic, or ischemic conditions. In particular, when the slices were incubated for 10 min at 32 degrees C under “ischemic” conditions (namely, lack of oxygen and glucose), endogenous aspartate and glutamate in the supernatant increased by 10 and 20 times, respectively. Since radical scavengers (D-mannitol), drugs reducing free radical formation (indomethacin, corticosteroid), or enzymes able to metabolize them (catalase and superoxide dismutase) significantly reduced this output, it was supposed that free radicals caused EAA release. A direct demonstration of this concept was obtained by showing a significant release of EAA after incubation of hippocampal slices with enzymes and substrates known to cause the formation of free radicals, such as xanthine plus xanthine oxidase or arachidonic acid plus prostaglandin synthase. Neither ischemia nor the enzymatic reactions leading to free radical production increased the activity of the cytoplasmic enzyme lactate dehydrogenase in the incubation medium, thus ruling out a nonspecific cellular lysis. It appears therefore that during ischemic states, brain production of reactive molecules (free radicals) causes an increased output of EAA. This may trigger a series of events which could help to explain the delayed loss of neurons after a transient ischemic period.

Aleph: a detector for electron-positron annihilations at Lep

Abstract: Process-centred Software Engineering Environments (PSEE) are the most recent generation of environments supporting software development activities. Most of PSEE are based on mechanisms promoting enforcement and automation of process activities. In this kind of mechanisms the process models are prescribed in a detailed and complete way. But the experience shows that supporting processes is more concerned with the flexibility of guidance offered during the process performance than with enforcement of a collection of predefined process models. In this paper, we present a solution to support strategic processes in a PSEE by providing a flexible guidance during process enactment.

Genetic linkage studies suggest that Alzheimer's disease is not a single homogeneous disorder

Abstract: Alzheimer's disease, a fatal neurodegenerative disorder of unknown aetiology, is usually considered to be a single disorder because of the general uniformity of the disease phenotype. Two recent genetic linkage studies revealed co-segregation of familial Alzheimer disease with the D21S1/S11 and D21S16 loci on chromosome 21. But two other studies, one of predominantly multiplex kindreds with a late age-of-onset, the other of a cadre of kindreds with a unique Volga German ethnic origin, found absence of linkage at least to D21S1/S11. So far it has not been possible to discern whether these conflicting reports reflect aetiological heterogeneity, differences in methods of pedigree selection, effects of confounding variables in the analysis (for example, diagnostic errors, assortative matings), or true non-replication. To resolve this issue, we have now examined the inheritance of five polymorphic DNA markers from the proximal long arm of chromosome 21 in a large unselected series of pedigrees with familial Alzheimer's disease. Our data suggest that Alzheimer's disease is not a single entity, but rather results from genetic defects on chromosome 21 and from other genetic or nongenetic factors.

The contractile response during steady lengthening of stimulated frog muscle fibres.

Abstract: 1. Steady lengthenings at different velocities (0.025-1.2 microns/s per half-sarcomere; temperature 2-5.5 degrees C) were imposed on isolated frog muscle fibres at the isometric tetanus plateau by means of a loudspeaker motor. The lengthening at the sarcomere level was measured by means of a striation follower either in fixed-end or in length-clamp mode. The force response was measured by a capacitance gauge transducer (resonance frequency 50 kHz). Preparations showing gross non-homogeneity during lengthening were excluded. 2. A steady tension was in all cases reached after about 20 nm per half-sarcomere of lengthening. Tension during this steady phase rose with speed of elongation up to 0.25-0.4 micron/s per half-sarcomere, when tension was 1.9-2 times isometric tetanic force (T0). Further increase in speed produced only very little increase in the steady tension. 3. During the transitory phase, before steady tension was reached, the tension rose monotonically if speed of lengthening was less than 0.25-0.3 micron/s per half-sarcomere; at higher speed the tension rose above the steady level, reaching a peak when extension was 10-14 nm per half-sarcomere, and then fell to the steady level. Tension at the peak continued to rise with speed of lengthening above 0.3 micron/s per half-sarcomere. 4. During the tension rise within the transitory phase of force response the segment elongated at a speed 15-20% lower than that imposed on the whole fibre, as a consequence of tendon compliance. 5. During the steady phase, non-homogeneity of lengthening speed began above a speed of lengthening which varied from fibre to fibre. At speeds below this value, segments elongated at the same speed as that imposed on the fibre. 6. Tension responses to large step stretches (up to 12 nm per half-sarcomere), applied at the plateau of isometric tetanus, showed that the instantaneous elasticity of contractile machinery is not responsible for the limit in force attained with high-speed lengthening. 7. Instantaneous stiffness was determined during the steady state of force response by superposing small steps (less than 1.5 nm per half-sarcomere) on steady lengthening at different velocities. Stiffness was 10-20% larger during lengthening than at the plateau of isometric tetanus and remained practically constant, independent of lengthening velocity, in the range of velocities used. 8. The results indicate that steady lengthening of a tetanized fibre induces a cross-bridge cycle characterized by fast detachment of the cross-bridge extended beyond a critical level.(ABSTRACT TRUNCATED AT 400 WORDS)

Prevalence of clinically diagnosed Alzheimer's disease and other dementing disorders: a door-to-door survey in Appignano, Macerata Province, Italy.

Abstract: The purpose of this study was to investigate the prevalence of dementia in an Italian population using a door-to-door 2-phase design. As part of a social and health survey, we administered the Hodkinson abbreviated mental test to all persons over age 59 residing in the Commune of Appignano on January 1, 1987 (N = 778). We then investigated all subjects scoring 7 or less on the cognitive test following a standardized diagnostic protocol. We found 48 patients affected by dementia, yielding a crude prevalence ratio (cases per 100 population over age 59) of 6.2; prevalence ratios were 2.6 for Alzheimer9s disease, 2.2 for multi-infarct dementia, 0.8 for mixed dementia, 0.4 for secondary dementia, and 0.3 for unspecified dementia. Age- and sex-specific prevalence ratios increased steeply with age and were consistently higher in women for Alzheimer9s disease and in men for dementia of all types and multi-infarct dementia. Alzheimer9s disease was slightly more frequent than multi-infarct dementia; however, the most common type of dementia varied across age groups. Most cases of Alzheimer9s disease were sporadic and had a late age of onset. Comparison with other populations suggests that dementia of all types is as frequent in Appignano as elsewhere, and that Alzheimer9s disease might be more frequent in rural than in urban populations.

A case-control study of gastric cancer and diet in Italy: II. Association with nutrients

Abstract: A case-control study involving interviews with 1,016 gastric cancer (GC) patients and 1,159 population-based controls in high- and low-risk areas was conducted to evaluate dietary factors and their contribution to the marked geographic variation in mortality from this cancer within Italy. Risks of GC were found to vary significantly with estimated nutrient intake. Risk rose with increasing consumption of nitrites and protein, and decreased in proportion to intake of ascorbic acid, beta-carotene, alpha-tocopherol, and vegetable fat. The associations with nitrite and beta-carotene tended to fade, however, in multivariate analyses adjusting for intake of other nutrients. Ascorbic acid showed the strongest geographic gradient, with highest consumption in low-risk areas. The findings suggest that the protective effects we previously reported for consumption of fresh fruit, fresh vegetables and olive oil may be linked to the vitamins C and E contained in these foods. The findings are consistent with the hypothesis that N-nitroso compounds are involved in GC risks, since elevated risks were apparent for agents (nitrites, protein) that promote nitrosation, while decreased risks were found for nutrients (ascorbic acid and alpha-tocopherol) which inhibit the process.

Interleukin 1 is an autocrine regulator of human endothelial cell growth.

Abstract: Proliferation of endothelial cells is regulated through the autocrine production of growth factors and the expression of cognate surface receptors. In this study, we demonstrate that interleukin 1 (IL-1) is an inhibitor of endothelial growth in vitro and in vivo. IL-1 arrested growing, cultured endothelial cells in G1 phase; inhibition of proliferation was dose dependent and occurred in parallel with occupancy of endothelial surface IL-1 receptors. In an angiogenesis model, IL-1 could inhibit fibroblast growth factor-induced vessel formation. The autocrine nature of the IL-1 effect on endothelial proliferation was demonstrated by the observation that occupancy of cell-surface receptors by endogenous IL-1 depressed cell growth. The potential significance of this finding was emphasized by the detection of IL-1 in the native endothelium of human umbilical veins. A mechanism by which IL-1 may exert its inhibitory effect on endothelial cell growth was suggested by studies showing that IL-1 decreased the expression of high-affinity fibroblast growth factor binding sites on endothelium. These results point to a potentially important role of IL-1 in regulating blood vessel growth and suggest that autocrine production of inhibitory factors may be a mechanism controlling proliferation of normal cells.

Measurement of pi 0 pi 0 production in two-photon collisions.

Abstract: The reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ has been analyzed using 97 ${\mathrm{pb}}^{\ensuremath{-}1}$ of data taken with the Crystal Ball detector at the DESY ${e}^{\ensuremath{-}}{e}^{+}$ storage ring DORIS II at beam energies around 5.3 GeV. For the first time we have measured the cross section for $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ for ${\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ mvariant masses ranging from threshold to about 2 GeV. We measure an approximately flat cross section of about 10 nb for $W={m}_{{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}}l0.8$ GeV, which is below 0.6 GeV, in good agreement with a theoretical prediction based on an unitarized Born-term model. At higher invariant masses we observe formation of the ${f}_{2}(1270)$ resonance and a hint of the ${f}_{0}(975)$. We deduce the following two-photon widths: ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}\ensuremath{\gamma}}({f}_{2}(1270))=3.19\ifmmode\pm\else\textpm\fi{}{0.16\ifmmode\pm\else\textpm\fi{}}_{0.28}^{0.29}$ keV and ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}\ensuremath{\gamma}}({f}_{0}(975))l0.53$ keV at 90% C.L. The decay-angular distributions show the ${\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ system to be dominantly spin 0 for $Wl0.7$ GeV and spin 2, helicity 2 in the ${f}_{2}(1270)$ region, with helicity 0 contributing at most 22% (90% C.L.).

Identification of localized redox states in plant-type two-iron ferredoxins using the nuclear Overhauser effect.

Abstract: The homonuclear Overhauser effect (NOE), in conjunction with nonselective spin-lattice relaxation measurements, has been employed to assign the contact-shifted resonances for the reduced form of two typical plant-type two-iron ferrodoxins from the algae Spirulina platensis and Porphyra umbilicalis. These results demonstrate that the NOE should have broad general applicability for the assignments and electronic structural elucidation of diverse subclasses of paramagnetic iron-sulfur cluster proteins. NOE connectivities were detected only among sets of resonances exhibiting characteristically different deviations from Curie behavior, providing strong support for the applicability of the spin Hamiltonian formulation for the NMR properties of the antiferromagnetically coupled iron clusters. The geminal {beta}-methylene protons for the two cysteines bound to the iron(II) center were clearly identified, as well as the C{sub {alpha}}H and one C{sub {beta}}H for each of the cysteines bound to the iron(III). The identification of the iron bound to cysteines 41 and 46 as the iron(II) in the reduced protein was effected on the basis of dipolar contacts between the bound cysteines. Resolved labile proton contact-shifted resonances are attributed to hydrogen bonding to the iron(III) center, and it is concluded that the contact-shifted resonances for the more numerous hydrogen bonds to the iron(II) center are notmore » resolved from the diamagnetic envelope. The identification of the iron closer to the protein surface as the more reducible one is consistent with predictions based on a larger number of hydrogen bonds to this center.« less

NK1‐receptors mediate the proliferative response of human fibroblasts to tachykinins

Abstract: 1. The effect of synthetic tachykinin selective receptor agonists was studied on the growth of cultured human skin fibroblasts (HF). 2. Human fibroblasts were grown in serum-free conditions in the presence of natural tachykinins (substance P and neurokinin A) and of three synthetic agonists, [beta-Ala4, Sar9, Met(O2)11]-SP(4-11), [beta-Ala8]-NKA(4-10) and [MePhe7]-NKB selective for NK1-, NK2- and NK3-receptors respectively. Cell proliferation was measured by percentage increase in cell number and by [3H]-thymidine uptake following 48 h exposure to agents compared to baseline condition. 3. Neurokinin A (NKA) and substance P (SP) significantly increased cell proliferation the threshold concentrations being 10(-12) and 10(-11) M, respectively. Addition of thiorphan to culture conditions enhanced the effect of SP but not of NKA. 4. The selective NK1-receptor agonist produced a dose-dependent increase in cell proliferation as judged by total cell number and [3H]-thymidine uptake. No significant effect was observed with NK2- and NK3-receptor agonists. 5. These data indicate that the effect of SP on fibroblast proliferation is mediated by interaction with a NK1-receptor type and local metabolism can interfere with the full expression of this effect of SP on cell proliferation.

Human myometrium during pregnancy contains and responds to V1 vasopressin receptors as well as oxytocin receptors.

Abstract: We have recently demonstrated the presence of two classes of neurohypophysial hormone receptors in the vagina, myometrium, and oviduct of rabbit: an oxytocin (OT) site and a VI arginine vasopressin (AVP) site. We now report binding and in vitro contractility studies on human myometrial specimens obtained at cesarean section from women at the end of pregnancy. The program Ligand was used to analyze self- and cross-displacement curves for labeled OT, AVP or its VI antagonist d(CH2)5TyrMeAVP, the corresponding unlabeled peptides, and selective analogs. Our results clearly indicate the presence of heterogeneity of binding sites in human uterus. Blocking experiments were performed to evaluate the density of OT and VI AVP receptors in individual uterine specimens. The contractile response of the same samples to OT, AVP, and analogs was also evaluated. Our results indicate that VI AVP receptors are present in all of the uterine specimens investigated, with virtually equal density from 32 weeks to term. AVP and t...

Racial differences in the anterior circulation in cerebrovascular disease. How much can be explained by risk factors

Abstract: • The entry characteristics of 1367 patients enrolled into the Extracranial/Intracranial Bypass Study were examined to determine if site differences in intracranial and extracranial arterial lesions among racial groups could be explained by differences in risk factors. Blacks were more often hypertensive, diabetic, or cigarette smokers, while whites had higher systolic blood pressure and hemoglobin values. Orientals had the lowest prevalence of vascular risk factors. Despite these differences in risk factors, multivariate analysis showed race to be an independent and strong predictor of the location of cerebrovascular lesions. To our knowledge, this study is unique in documenting risk factors prospectively and systematically in three racial groups simultaneously. Although generalization is limited by possible biases related to patient selection, the results affirm previous tentative conclusions about the role of race in determining the location of cerebrovascular disease.

A distance for similarity classes of submanifolds of a Euclidean space

Abstract: A distance is defined on the quotient of the set of submanifolds of a Euclidean space, with respect to similarity. It is then related to a previously defined function which captures the metric behaviour of paths.

A multicentre follow-up study of 1152 patients with myasthenia gravis in Italy

Abstract: A multicentre retrospective study was carried out on the characteristics and course of myasthenia gravis (MG) in Italy. Data from 1152 patients, fairly representative of the myasthenic population seeking medical advice, were analysed for diagnostic criteria, clinical aspects and therapeutic approaches. Mean follow-up was 4.9 years. The disease was correctly diagnosed within 2 years of the onset in 80% of cases. Onset of symptoms peaked in the second and third decade in females and fell between 20 and 59 years in males. At first observation 87% of the patients had generalized MG. Maximal worsening was observed within 3 years in 77% of patients. At the last follow-up, 35% of cases were symptom-free (pharmacological remission 24%, remission without treatment 11%). The more severe the disease at the first observation and at the maximal worsening of symptoms, the lower was the proportion of remissions. Steroids were given in 54% and immunosuppressants in 18%. Thymectomy was performed in 72%, mostly in women, younger than age 40, and with generalized MG. Thymectomy seemed to improve the course of the disease, mostly in patients operated on shortly after diagnosis and those with generalized mild-to-moderate disease and with a normally involuted thymus. MG was lethal in 4% of patients, principally men, older than 40, in grade 3 or worse at first observation, with a short history of disease, and with thymona.