Showing papers by "University of Coimbra published in 2000"

Ubiquitinated Sperm Mitochondria, Selective Proteolysis, and the Regulation of Mitochondrial Inheritance in Mammalian Embryos

Abstract: The strictly maternal inheritance of mitochondria and mitochondrial DNA (mtDNA) in mammals is a developmental paradox promoted by an unknown mechanism responsible for the destruction of the sperm mitochondria shortly after fertilization. We have recently reported that the sperm mitochondria are ubiquitinated inside the oocyte cytoplasm and later subjected to proteolysis during preimplantation development (P. Sutovsky et al., Nature 1999; 402:371-372). Here, we provide further evidence for this process by showing that the proteolytic destruction of bull sperm mitochondria inside cow egg cytoplasm depends upon the activity of the universal proteolytic marker, ubiquitin, and the lysosomal apparatus of the egg. Binding of ubiquitin to sperm mitochondria was visualized by monospecific antibodies throughout pronuclear development and during the first embryonic divisions. The recognition and disposal of the ubiquitinated sperm mitochondria was prevented by the microinjection of anti-ubiquitin antibodies and by the treatment of the fertilized zygotes with lysosomotropic agent ammonium chloride. The postfecundal ubiquitination of sperm mitochondria and their destruction was not seen in the hybrid embryos created using cow eggs and sperm of wild cattle, gaur, thus supporting the hypothesis that sperm mitochondrion destruction is species specific. The initial ligation of ubiquitin molecules to sperm mitochondrial membrane proteins, one of which could be prohibitin, occurs during spermatogenesis. Even though the ubiquitin cross-reactivity was transiently lost from the sperm mitochondria during epididymal passage, likely as a result of disulfide bond cross-linking, it was restored and amplified after fertilization. Ubiquitination therefore may represent a mechanism for the elimination of paternal mitochondria during fertilization. Our data have important implications for anthropology, treatment of mitochondrial disorders, and for the new methods of assisted procreation, such as cloning, oocyte cytoplasm donation, and intracytoplasmic sperm injection.

Stator winding fault diagnosis in three-phase synchronous and asynchronous motors, by the extended Park's vector approach

Abstract: This paper describes the use of the extended Park's vector approach (EPVA) for diagnosing the occurrence of stator winding faults in operating three-phase synchronous and asynchronous motors. The major theoretical principles related with the EPVA are presented and it is shown how stator winding faults can be effectively diagnosed by the use of this noninvasive approach. Experimental results, obtained in the laboratory, corroborate that these faults can be detected, in the EPVA signature, by the identification of a spectral component at twice the fundamental supply frequency. On-site tests, conducted in a power generation plant and in a cement mill, demonstrate the effectiveness of the EPVA in the detection of stator circuit faults in large industrial motors, rated up to 5 MW.

An Introduction to Pidgins and Creoles

Abstract: This textbook is a clear and concise introduction to the study of how new languages come into being. Starting with an overview of the field's basic concepts, it surveys the new languages that developed as a result of the European expansion to the Americas, Africa, Asia and the Pacific. Long misunderstood as 'bad' versions of European languages, today such varieties as Jamaican Creole English, Haitian Creole French and New Guinea Pidgin are recognized as distinct languages in their own right. John Holm examines the structure of these pidgins and creoles, the social history of their speakers, and the theories put forward to explain how their vocabularies, sound systems and grammars evolved. His new findings on structural typology, including non-Atlantic creoles, permit a wide-ranging assessment of the nature of restructured languages worldwide. This much-needed book will be welcomed by students and researchers in linguistics, sociolinguistics, western European languages, anthropology and sociology.

Characterisation of Ti1−xSixNy nanocomposite films

Abstract: Ti 1− x Si x N y films were synthesised by RF reactive sputtering from Ti and Si elemental targets, in an Ar/N 2 gas mixture. XRD results revealed the development of a two-phase system, composed of a nanocrystalline f.c.c. TiN (phase 1: B1 NaCl type) and a second one (phase 2), where Si atoms replaced some of the Ti ones, inducing a structure that we may call a solid solution. An amorphous phase, supposed to be of silicon nitride, within grain boundaries seems to be also present, especially for high Si contents. TEM experiments confirmed the f.c.c.-type structure for phase 2, which is the only phase that develops without ion bombardment. The higher lattice parameter of phase 1 (∼0.429 nm compared to 0.424 nm for bulk TiN) may be explained by the residual stress effect on peak position. The Ti replacement by Si would explain the low value of the lattice parameter for phase 2 (∼0.418 nm). All samples showed good results for hardness (Hv≥30 GPa), and Ti 0.85 Si 0.15 N 1.03 at a deposition temperature of 300°C showed a value of approximately 47 Gpa, which is approximately double that of pure TiN. For higher deposition temperatures, an increase in hardness is observed, as demonstrated by this same sample, which at 400°C reveals a value of approximately 54 GPa. Similar behaviour was observed in adhesion, where this same sample revealed a critical load for adhesive failure of approximately 90 N. In terms of oxidation resistance, a significant increase has also been observed in comparison with TiN. At 600°C, the oxidation resistance of Ti 0.70 Si 0.30 N 1.10 is already 100 times higher than that of TiN. For higher temperatures this behaviour tends to be even better when compared with other nitrides.

Inhibition of human LDL lipid peroxidation by phenol-rich beverages and their impact on plasma total antioxidant capacity in humans.

Abstract: Mounting evidence shows that phenol-rich beverages exert strong antioxidant activity. However, in vivo evidence has produced conflicting results. In the present study, we studied the impact of the ingestion of 300 mL of black and green tea, alcohol-free red wine, alcohol-free white wine, or water on plasma total antioxidant capacity in five healthy volunteers. Red wine has the highest content of phenolics (3.63 ± 0.48 g QE/L), followed by green tea (2.82 ± 0.07 g QE/L), black tea (1.37 ± 0.15 g QE/L), and white wine (0.31 ± 0.01 g QE/L). Plasma total antioxidant capacity values of subjects who drank green tea rose at 30 min (P < 0.05). After black tea and red wine ingestion, the peaks were at 50 min (P < 0.05 and P < 0.01, respectively). No changes were observed in the control and white wine groups. Red wine and green tea were the most efficient in protecting low density lipoprotein from oxidation driven by peroxyl and ferril radicals, respectively. Phenol-rich beverages are a natural source of antioxidants; however, the phenolic content alone cannot be considered an index of their in vivo antioxidant activity.

On the emulation of software faults by software fault injection

Abstract: This paper presents an experimental study on the emulation of software faults by fault injection. In a first experiment, a set of real software faults has been compared with faults injected by a SWIFI tool (Xception) to evaluate the accuracy of the injected faults. Results revealed the limitations of Xception (and other SWIFI tools) in the emulation of different classes of software faults (about 44% of the software faults cannot be emulated). The use of field data about real faults was discussed and software metrics were suggested as an alternative to guide the injection process when field data is nor available. In a second experiment, a set of rules for the injection of errors meant to emulate classes of software faults was evaluated. The fault triggers used seem to be the cause for the observed strong impact of the faults in the target system and in the program results. The results also show the influence in the fault emulation of aspects such as code size, complexity of data structures, and recursive versus sequential execution.

Electrochemical Oxidation of 8-Oxoguanine

Abstract: Electrochemical oxidation of DNA can occur at each of the four bases and guanine is the one that can suffer the easiest oxidative damage. The occurrence of the guanine oxidation product, 8-oxoguanine, as a consequence of DNA damage caused by DNA oxidation causes important mutagenic lesions and hence it is very important to develop reliable methods for its quantification. Electrochemical study of the mechanism of oxidation of 8-oxoguanine on glassy carbon shows that it is a reversible electrode process, pH dependent, and involves several reaction products. Electroanalytical determinations of 8-oxoguanine were carried out and the detection limit was 8×10–7 M.

Green's Functions for Two-and-a-Half-Dimensional Elastodynamic Problems

Abstract: This paper presents a fully analytical solution, together with explicit expressions, for the steady-state response of a homogeneous 3D space subjected to a spatially sinusoidal, harmonic line load. In the literature, this problem is often referred to as the two-and-a-half-dimensional \Ifundamental solution\N or two-and-a-half-dimensional Green’s functions. These equations are of great usefulness in the formulation of 3D elastodynamic problems by means of integral transforms methods and/or boundary elements. The final expressions are validated here by applying the equations to the problem of a 3D point load, for which the solution is known in analytical form.

[Development of the Portuguese version of MOS SF-36. Part I. Cultural and linguistic adaptation].

Abstract: No one aims at applying generic measures as substitutes for other more traditional clinical procedures. The whole history of the evolution of these types of measures has been based on comparisons with clinical measures, always seen by researchers as ways to validate health outcome measures and as a process to be recognized by clinicians as a way to detect changes in time not always detected by the usual measures. The measurement instrument presented in this paper is the Portuguese version of the MOS SF-36, originally a result of the Medical Outcomes Study, a study carried out by Rand Corporation researchers in the 80's. One of the objectives of these researchers was precisely to develop instruments to be used in continuous monitoring of outcomes. This paper describes the first time MOS SF-36 was culturally adapted to Portuguese, validated and implemented. The first part mentions some of the foundations and developments of the original instrument as well as some results obtained from some specific applications. The second part introduces operational definitions for each of the eight scales and describes the SF-36 measurement model as well as the factor structure with two dimensions. Next, we present the design used by us to transform the data from the time they are collected from the respondents to the time they are ready to be further used. Finally, the methodology used to culturally adapt the MOS SF-36 and create a Portuguese version which is culturally equivalent are presented.

Development of the Portuguese version of MOS SF-36. Part II --Validation tests.

Abstract: This paper describes the study aimed at validating the Portuguese version of the MOS SF-36 instrument of assessment. It starts by presenting the results of the implementation of this instrument in a sample of 930 pregnant women and the results of scaling tests, including the values of internal consistency and reliability. However, since a reliable instrument is not necessarily a valid one, the results of several validity tests are also presented. Finally, this paper ends by recommending the use of the Portuguese version of the SF-36 instrument of assessment.

Vesicular Traffic and Golgi Apparatus Dynamics During Mammalian Spermatogenesis: Implications for Acrosome Architecture

Abstract: Vesicular membrane trafficking during acrosome biogenesis in bull and rhesus monkey spermatogenesis differs from the somatic cell paradigm as imaged dynamically using the Golgi apparatus probes b-COP, giantin, Golgin-97, and Golgin-95/ GM130. In particular, sorting and delivery of proteins seemed less precise during spermatogenesis. In early stages of spermiogenesis, many Golgi resident proteins and specific acrosomal markers were present in the acrosome. Trafficking in both round and elongating spermatids was similar to what has been described for somatic cells, as judged by the kinetics of Golgi protein incorporation into endoplasmic reticulum-like structures after brefeldin A treatment. These Golgi components were retrieved from the acrosome at later stages of differentiation and were completely devoid of immature spermatozoa. Our data suggest that active anterograde and retrograde vesicular transport trafficking pathways, involving both b-COP- and clathrincoated vesicles, are involved in retrieving Golgi proteins missorted to the acrosome and in controlling the growth and shape of this organelle. gametogenesis, sperm, spermatid, spermatogenesis, testes

Additive aggregation with variable interdependent parameters: the VIP Analysis software

Abstract: We consider the aggregation of multicriteria performances by means of an additive value function under imprecise information. The problem addressed here is the way an analysis may be conducted when the decision makers are not able to (or do not wish to) fix precise values for the importance parameters. These parameters can be seen as interdependent variables that may take several values subject to constraints. Firstly, we briefly classify some existing approaches to deal with this problem. We argue that they complement each other, each one having its merits and shortcomings. Then, we present a new decision support software—VIP analysis—which incorporates approaches belonging to different classes. It proposes a methodology of analysis based on the progressive reduction of the number of alternatives, introducing a concept of tolerance that lets the decision makers use some of the approaches in a more flexible manner.

ELECTRE TRI for Groups with Imprecise Information on Parameter Values

Abstract: ELECTRE TRI is a well-known method to assign actions to predefined ordered categories, considering multiple criteria. Using this method requires setting many parameters, which is often a difficult task. We consider the case where a group of Decision Makers (DMs) is unsure of which values each parameter should take, which may result from insufficient, imprecise or contradictory information, as well as from lack of consensus among the group members. In a framework where DMs provide constraints bounding and interrelating the parameter values, rather than fixing precise figures, we discuss the problem of finding the best and worst category that each action may attain.

Grazing rates of organic matter and living fungal biomass of decaying Spartina alterniflora by three species of salt-marsh invertebrates

Abstract: The pathway for the flow of salt-marsh grass production into marsh food-webs is still not well defined. We compared the abilities of three marsh macroinvertebrates [salt marsh periwinkles, Littoraria irrorata (Say) (=Littorina irrorata), salt-marsh coffee-bean snails, Melampus bidentatus (Say); and a talitrid amphipod, Uhlorchestia spartinophila Bounsfield and Heard] to access standing-dead leaves of smooth cordgrass (Spartina alterniflora Loisel). The invertebrates were incubated with naturally-decaying leaves, and the rates of removal of organic matter and living fungal biomass (ergosterol) were measured. The impact of invertebrate activity upon fungal growth rates was measured as rates of fungal-membrane synthesis (incorporation of radioacetate into ergosterol). The removal rates of organic leaf biomass per mg individual biomass were highest for amphipods (700 μg mg−1 d−1) and lowest for periwinkles (90 μg mg−1 d−1), but the relatively large biomass of the snails made their removal rates per individual greater than those of amphipods. Net removal of ergosterol by all three invertebrates was >50% for yellow-brown (early-decay) leaf blades. For fully-brown (advanced-decay) blades, >50% removal of ergosterol was found only for periwinkles; exposure to coffee-bean snails and amphipods resulted in a net ergosterol reduction of ≤20%. The lower net reduction of living fungal biomass by coffee-bean snails and amphipods may have been due to fungal-growth stimulation (2.3-fold stimulation in coffee-bean snails and 1.5-fold stimulation in amphipods). Grazing by periwinkles did not stimulate fungal growth, possibly because of its high intensity. Grazing by these three salt-marsh shredders may affect marsh-grass shoot-decay in different ways. Periwinkles may abbreviate the period of fungal production, and incorporate the decaying material relatively quickly into snail biomass and fecal-pellet rain to the sediments. Coffee-bean snails and amphipods may enhance and prolong fungal production, along with the formation of fecal-pellet rain. All three invertebrates fed preferentially on leaf blades rather than leaf sheaths, and feeding rates of gastropods were higher during the night than during the day.

Regulation of AMPA receptors by phosphorylation.

Abstract: The AMPA receptors for glutamate are oligomeric structures that mediate fast excitatory responses in the central nervous system. Phosphorylation of AMPA receptors is an important mechanism for short-term modulation of their function, and is thought to play an important role in synaptic plasticity in different brain regions. Recent studies have shown that phosphorylation of AMPA receptors by cAMP-dependent protein kinase (PKA) and Ca2+ - and calmodulin-dependent protein kinase II (CaMKII) potentiates their activity, but phosphorylation of the receptor subunits may also affect their interaction with intracellular proteins, and their expression at the plasma membrane. Phosphorylation of AMPA receptor subunits has also been investigated in relation to processes of synaptic plasticity. This review focuses on recent advances in understanding the molecular mechanisms of regulation of AMPA receptors, and their implications in synaptic plasticity.

An unstable trinucleotide-repeat region on chromosome 13 implicated in spinocerebellar ataxia: A common expansion locus

Abstract: Larger CAG/CTG trinucleotide-repeat tracts in individuals affected with schizophrenia (SCZ) and bipolar affective disorder (BPAD) in comparison with control individuals have previously been reported, implying a possible etiological role for trinucleotide repeats in these diseases. Two unstable CAG/CTG repeats, SEF2-1B and ERDA1, have recently been cloned, and studies indicate that the majority of individuals with large repeats as detected by repeat-expansion detection (RED) have large repeat alleles at these loci. These repeats do not show association of large alleles with either BPAD or SCZ. Using RED, we have identified a BPAD individual with a very large CAG/CTG repeat that is not due to expansion at SEF2-1B or ERDA1. From this individual's DNA, we have cloned a highly polymorphic trinucleotide repeat consisting of (CTA)n (CTG)n, which is very long ( approximately 1,800 bp) in this patient. The repeat region localizes to chromosome 13q21, within 1.2 cM of fragile site FRA13C. Repeat alleles in our sample were unstable in 13 (5.6%) of 231 meioses. Large alleles (>100 repeats) were observed in 14 (1. 25%) of 1,120 patients with psychosis, borderline personality disorder, or juvenile-onset depression and in 5 (.7%) of 710 healthy controls. Very large alleles were also detected for Centre d'Etude Polymorphisme Humaine (CEPH) reference family 1334. This triplet expansion has recently been reported to be the cause of spinocerebellar ataxia type 8 (SCA8); however, none of our large alleles above the disease threshold occurred in individuals either affected by SCA or with known family history of SCA. The high frequency of large alleles at this locus is inconsistent with the much rarer occurrence of SCA8. Thus, it seems unlikely that expansion alone causes SCA8; other genetic mechanisms may be necessary to explain SCA8 etiology.

Contact fatigue of automotive gears: evolution and effects of residual stresses introduced by surface treatments

Abstract: Helical gears from an automotive gearbox, previously subjected to the surface treatments of carbo-nitriding and shot-peening, were submitted to contact fatigue tests. The X-ray diffraction technique was used to characterize the evolution of different mechanical and metallurgical parameters as a function of gear damage. Particular attention was paid to residual stress relief. A numerical model was developed to predict residual stress relaxation and estimate the most likely localization of contact fatigue crack initiation. The stress–strain laws of the surface-treated layers were determined by means of two separate experimental methods, based on locally measured parameters. The Dang Van multiaxial fatigue criterion was used to analyse the failure of the gears, taking into account the effects of friction and roughness.

Fault-tolerant execution of mobile agents

Abstract: In this paper, we will address the list of problems that have to be solved in mobile agent systems and we will present a set of fault-tolerance techniques that can increase the robustness of agent-based applications without introducing a high performance overhead. The framework includes a set of schemes for failure detection, checkpointing and restart, software rejuvenation, a resource-aware atomic migration protocol, a reconfigurable itinerary, a protocol that avoids agents to get caught in node failures and a simple scheme to deal with network partitions. At the end, we will present some performance results that show the effectiveness of these fault-tolerance techniques.

Alicyclobacillus hesperidum sp. nov. and a related genomic species from solfataric soils of São Miguel in the Azores.

Abstract: Several acidophilic, slightly thermophilic or thermophilic Gram-positive isolates were recovered from solfataric soil at Furnas on the Island of Sao Miguel in the Azores. Phylogenetic analysis of the 16S rRNA gene sequence showed that these organisms represented two novel species of the genus Alicyclobacillus. Strains FR-11T and FR-1b had an optimum growth temperature of about 50 degrees C, whereas strains FR-3 and FR-6T had an optimum growth temperature of about 60 degrees C. Biochemical, physiological and chemotaxonomic characteristics did not distinguish isolates FR-3 and FR-6T from the type strain of Alicyclobacillus acidocaldarius; however, strains FR-11T and FR-1b could be easily distinguished from the type strain of Alicyclobacillus acidoterrestris by the carbon source assimilation pattern and the fatty acid composition. On the basis of the phylogenetic analysis, physiological and biochemical characteristics, and fatty acid composition the name Alicyclobacillus hesperidum is proposed for the species represented by strains FR-11T and FR-1b; a formal name for the new genomic species represented by strains FR-3 and FR-6T is not proposed at this time.