Showing papers by "University of Lisbon published in 1995"

A Controlled Trial of Zidovudine in Primary Human Immunodeficiency Virus Infection

Abstract: Background It is possible that antiretroviral treatment given early during primary infection with the human immunodeficiency virus (HIV) may reduce acute symptoms, help preserve immune function, and improve the long-term prognosis. Methods To assess the effect of early antiviral treatment, we conducted a multicenter, double-blind, placebo-controlled trial in which 77 patients with primary HIV infection were randomly assigned to receive either zidovudine (250 mg twice daily; n = 39) or placebo (n = 38) for six months. Results The mean time from the onset of symptoms until enrollment in the study was 25.1 days. Among the 43 patients who were still symptomatic at the time of enrollment, there was no appreciable difference in the mean (±SE) duration of the retroviral syndrome between the zidovudine group (15.0±4.1 days) and the placebo group (15.8±3.6 days). During a mean follow-up period of 15 months, minor opportunistic infections developed in eight patients: oral candidiasis in four, herpes zoster in two, ...

Ion dynamics and its possible role during in vitro pollen germination and tube growth

Abstract: One of the most interesting aspects of plant fertilization is the growth and orientation of the pollen tube from the stigma to the ovary. Considerable research has been carried out in this field but little is yet known about the mechanisms involved in the growth process. Recent research has been focused on the regulation of molecular events in order to discover the specific genes involved in tube growth. Important results in the biochemical and physiological aspects of molecular regulation have been reported. The following review attempts to cover these aspects. It is primarily based on talks presented by the authors at the 13th International Congress on Sexual Plant Reproduction and is mainly addressed to non-experts in the fields of electrophysiology and ion signalling. We aim to present a general overview of electrical currents, ion dynamics, and ion transporters in pollen, and their possible role during pollen tube germination and growth. Together with results on other tip-growing cells, a general model of pollen tube germination and growth as a self-organizing process is proposed.

Tsunami sedimentation associated with the Lisbon earthquake of 1 November AD 1755: Boca do Rio, Algarve, Portugal

Abstract: A description is given of a distinctive marine deposit at Boca do Rio on the Algarve coast of Portugal. It is proposed here that the sediment accumulation was deposited by the tsunami generated by the Lisbon earthquake of 1 November, AD 1755. The deposit exhibits sedimentary characteristics quite unlike other coastal sediment accumulations that are deposited by more moderate wave regimes. These include laterally continuous sand layers, chaotic pebble horizons, large amounts of gravel-sized shell debris and distinctive assemblages of marine microfossils. A preliminary attempt is made here to use the empirical field and laboratory data to define more clearly the processes of coastal sedimentation that characterize tsunami runup. The use of tsunami sediments as time synchronous marker horizons is also discussed.

Large-scale circulation regimes and surface climatic anomalies over the Mediterranean

Abstract: Significant relationships between atmospheric circulation anomalies, in terms of monthly mean 500 hPa geopotential height (Z500) and sea-level pressure (SLP) over Atlantic-Europe, and surface climatic anomalies, in terms of monthly rainfall (Rm) and monthly mean temperature (Tm), over the extended Mediterranean area, are examined statistically by canonical correlation analysis (CCA), with time lags from zero to four months. At a confidence level of 99.99 per cent, CCA yields five pairs of patterns that describe simultaneous responses of the monthly rainfall field to anomalies of surface circulation (SLP). Between mid-tropospheric circulation (Z500) and rainfall fields, six concurrent CCA pairs were also identified to be significant at the same confidence level. From the synoptic point view, these results seem very reasonable. Six concurrent (hereafter lag 0) CCA pairs and one CCA pair for a lag of 1 month (hereafter lag 1) were identified for the Z500—Tm fields at the confidence level of 99 per cent. The SLP—Tm fields, also six concurrent CCA pairs and three pairs for lag 1, were found to be significant at the same confidence level. Quite similar temperature anomaly patterns are represented in the first CCA pairs of the Z500—Tm fields for both lag 0 and lag 1, and in the first lag-1 and second lag-0 CCA pairs of the SLP-Tm fields; the patterns of air temperature anomalies revealed in the third CCA pair of SLP—Tm fields for lag 1, as well as in the fourth concurrent CCA pairs of the Z500—Tm and SLP—Tm fields, also resemble each other. Similar temperature anomaly patterns can be found for other CCA pairs. These similarities reveal that some slow-changing processes in large-scale anomalies of atmosphere are responsible for producing the same type of temperature anomalies.

Role of carbohydrates in micropropagation of cork oak

Abstract: The influences of carbon sources, fructose, glucose, sorbitol and sucrose on shoot proliferation and in vitro rooting of cork oak (Quercus suber L.) were compared at a wide range of concentrations (1–6%, w/v). The highest number of shoots occurred on glucose-containing medium. Nevertheless, we have chosen 3% sucrose which induced a similar rate of proliferation but favoured shoot elongation, permitting an effectively higher number of shoots during transfers. Sorbitol and autoclaved fructose did not stimulate shoot proliferation. Adventitious root formation was strongly dependent on carbohydrate supply. Sorbitol and autoclaved fructose were completely ineffectively on rooting induction. Glucose was the most effective carbon source on rooting promotion followed by sucrose and filter-sterilized fructose. The rooting response induced by fructose was dependent on the sterilizing procedure. The number of adventitious roots produced per shoot increased with increasing glucose and sucrose concentration. The content of reducing sugars in leaves of proliferation cultures and in leaves and roots of rooted plantlets was more dependent on carbon concentration than on glucose or sucrose supplement. The results presented here show that carbohydrate requirements during cork oak micropropagation depend upon the phase of culture. Sucrose (3%) and glucose (4%) were the best carbon sources respectively during proliferation and rooting phases.

Genotoxicity of quercetin in the micronucleus assay in mouse bone marrow erythrocytes, human lymphocytes, V79 cell line and identification of kinetochore-containing (CREST staining) micronuclei in human lymphocytes

Abstract: Quercetin, a mutagenic flavonoid widely distributed in edible plants, was studied for the induction of micronuclei (MN). We have carried out the MN assay in bone marrow polychromatic erythrocytes in mice, in cytokinesis-blocked human lymphocytes and in cytokinesis-blocked V79 cells. MN assay in vitro was performed in the presence and in the absence of S9. To further extend the study, an antikinetochore antibody (CREST staining) was used to distinguish MN containing whole chromosomes (kinetochore positive) from those containing acentric fragments (kinetochore negative). When tested in vivo quercetin failed to induce micronuclei, a result which is in agreement with other published reports. When tested in vitro in V79 cells quercetin clearly induces micronuclei in the absence of S9 and also in the presence of S9 for the highest dose used. When tested in vitro in human lymphocytes quercetin shows a significant induction of micronuclei in the absence and in the presence of S9. The presence of S9 compared to its absence is not significant for any of the systems used. Both in the presence and absence of S9, quercetin appears to behave as a clastogenic agent in human lymphocytes inducing a significant majority of kinetochore-negative MN.

Spatio-temporal distribution of the microphytobenthic biomass in intertidal flats of Tagus Estuary (Portugal)

Abstract: A study on spatio-temporal distribution of microphytobenthos in intertidal zones of Tagus Estuary was carried out from 1990 to 1992. Near Lisbon, Portugal, Tagus Estuary is a shallow mesotidal estuary, covering an area of 320 km2. The intertidal area ranges from 20 to 40% of the total area and it is constituted mainly by mudflats. Intertidal flats are richly populated by microalgae, diatoms being the most important and ubiquitous group.

Vehicle Scheduling for Public Mass Transit — An Overview

Abstract: Vehicle scheduling always plays an important role in urban mass transit companies. Efficient schedules of a given timetable have a significant influence on the demand for vehicles and, hence, the demand for personnel. This means that the economic results of a urban mass transit company are closely linked to the planning activities in this area.

Downscaling GCM information to regional scales: a non-parametric multivariate regression approach

Abstract: The multivariate adaptive regression splines (MARS) model was used to capture the observed relationships between sea level pressure (SLP) anomalies over the Euro-Atlantic sector and the winter time (December–February) monthly rainfall at eight sites in Portugal; possible anthropogenic changes of the rainfall in a perturbed future climate were then estimated by using both the observed SLP-rainfall relationships, described by MARS models, and the GCM simulated SLP, taken from the output of the Hadley Centre Transient Climate Change Experiment (UKTR). Also, principal component analysis was carried out to reduce the dimensionality of the SLP data, and to assess the ability of the GCM in simulating the large-scale circulation; the first six principal components were retained as predictors in the MARS model. The MARS model were built up by using the data for 1946–1991 as the training set and that for 1901–1943 as the testing set, showing satisfactory prediction skills. It is concluded that the UKTR control simulation successfully reproduced main features of the large-scale circulation, but the observed relationship between SLP and the regional rainfall was not well preserved. With respect to the 54-year experiment of perturbed run, the MARS estimation of rainfall and the relevant direct GCM rainfall output possess similar multi-annual variations; however, there are substantial differences regarding details; the change in the area mean of winter time mean monthly rainfall in Portugal estimated by MARS (indirect GCM output) is about −12.7 mm per 54-year, and the relevant direct GCM output is −16.9 mm/54-year. This reduction tendency is consistent with previously reported findings respecting rainfall in the Iberian Peninsula, which were based on the MPI (Max-Planck Institute for Meteorology) transient simulations.

A 2n Constraint Formulation for the Capacitated Minimal Spanning Tree Problem

Abstract: In this paper we present a new formulation for the Capacitated Minimal Spanning Tree CMST problem. One advantage of the new formulation is that it is more compact in the number of constraints than a well-known formulation. Additionally, we show that the linear programming relaxation of both formulations produces optimal solutions with the same cost. We present a brief discussion concerning valid inequalities for the CMST which are directly derived from the new formulation. We show that some of the new inequalities are not dominated by some sets of facet-inducing inequalities for the CMST. We derive some Lagrangian relaxation-based methods from the new formulation and present computational evidence showing that reasonable improvements on the original linear programming bounds can be obtained if these methods are strengthened by the use of cutting planes. The reported computational results indicate that one of the methods presented in this paper dominates, in most of the cases, the previous best methods reported in the literature. The most significant improvements are obtained in the instances with the root in the corner.

Large-area 1D thin-film position-sensitive detector with high detection resolution

Abstract: The aim of this work is to present the main optoelectronic characteristics of large-area one-dimensional position-sensitive detectors (1D TFPSDs) based on amorphous silicon (a-Si) p-i-n diodes. From that, the device resolution, response time and detectivity (defined as being the reciprocal of the noise equivalent power pattern) are derived and discussed concerning the field of applications of the 1D TFPSDs.

Seasonal changes in lipid content and composition of the polychaete Nereis (Hediste) diversicolor

Abstract: The lipid content and composition of Nereis (Hediste) diversicolor O. F. Muller (Annelida, Polychaeta, Nereidae) a mud-dwelling, intertidal errant polychaete in the Tagus estuary (Portugal), were examined on the monthly basis by lipid extraction, TLC and capillary GC. In this estuary, N. diversicolor is by far the dominant species among polychaeta and the main food item in the natural diet of several flatfishes. The biochemical elucidation of its lipid structure and distribution throughout the year, described in this study, provides information not only about the physiological role of lipids in the animal under consideration but also about dietary fatty acid requirements of some flatfishes in the wild and under laboratory conditions. The total lipid content varied between a maximum of 19.3% lyophilized dry weight in February (4.4% fresh weight) and a minimum of 6.6% in August (1.9% fresh weight). The major lipid classes were triacylglycerol, phospholipid, free sterol, free fatty acid, sterol ester/wax ester and alkyldiacylglycerol. The fatty acid composition was rather unsaturated with a 1:2 mean ratio of n-3: n-6. The major fatty acids were C160:0, C18:1n-9, C18:2n-6, and C20:5n-3; there were smaller amounts of C180:0, C18:1n-11, C18:1n-7, C18:3n-3, C20:1, C20:2n-6, C20:4n-6, C22:2, C22:5n-3, and many other fatty acids were detected at trace levels. The unsaturation ranged from 36.9 mg/g dry weight in summer to 107.4 mg/g in winter. An accumulation of fatty acids from plant origin was evident, in particular linoleic acid (C18:2n-6), which was quantitatively one of the major fatty acids throughout the year.

Direct evidence of meddy formation off the southwestern coast of Portugal

Abstract: The formation of a Mediterranean Water eddy, or meddy, was observed directly for the first time off the southwestern coast of Portugal near Cape St. Vincent. The formation event is revealed in the 30-day trajectory of a RAFOS float deployed in the lower core of the Mediterranean Undercurrent in the Gulf of Cadiz. For the first several days after deployment, this float was advected westward in the Undercurrent at a speed of about 0.4 m s −1 , generally paralleling the topography. Just after passing Cape St. Vincent, where the coast turns abruptly northward, the float began looping anticyclonically, indicating that it had become trapped in the core of a new meddy. The meddy translated first westward, then southwestward along the southern flank of Gorringe Bank. The float rotated around the meddy center with azimuthal speeds of 0.20–0.25 m s −1 at a radius of about 10 km. The rotation period was on the order of three days, and the average translation speed of the meddy over 25 days was 0.08 m s -1 . Observations of this and four additional 30-day trajectories indicate (1) persistent westward flow of the Undercurrent along the south coast of Portugal, (2) a tendency for the lower core of the Undercurrent to separate from the continental boundary after passing Cape St. Vincent, and (3) evidence of anticyclonic looping west of Cape St. Vincent. These preliminary results confirm the speculation that the region off Cape St. Vincent is one site of meddy generation.

In vitro and in vivo antitumor activity of benzyl isothiocyanate: a natural product from Tropaeolum majus.

Abstract: Cultured cells of Tropaeolum majus produce significant amounts of benzyl glucosinolate which, through enzymatic hydrolysis, results in the production of benzyl isothiocyanate (BITC). This study reports on the in vitro anticancer properties of BITC against a variety of human and murine tumor cell lines by four independent methods; SRB, MTT, cell counting, and clonogenic assays. Regardless of the assay used, BITC showed promising cytotoxicity in the low micromolar range (0.86 to 9.4 microM) against four human ovarian carcinoma cell lines (SKOV-3, 41-M, CHl, CHlcisR), a human lung tumor (H-69), a murine leukemia (L-1210), and a murine plasmacytoma (PC6/sens). The L1210 cells were most sensitive. BITC administered to mice bearing the ADJ/PC6 plasmacytoma subcutaneous tumor showed toxic effects at a dose of 200 mg/kg (within 24 h of drug administration) but no reduction in tumor mass. However, the growth inhibitory properties of BITC against a range of tumor cell types warrant further in vivo anti-tumor evaluation as well as its biotechnological production.

Gas exchange and carbon isotope discrimination in lichens: Evidence for interactions between CO2-concentrating mechanisms and diffusion limitation

Abstract: The characteristics of gas exchange and carbon isotope discrimination were determined for a number of lichen species, representing contrasting associations between fungal (mycobiont) and photosynthetic (photobiont) organism. These parameters were evaluated with regard to the occurrence of any CO2-concentrating mechanism (CCM) expressed specifically by the green algal (phycobiont) or cyanobacterial (cyanobiont) partner. Carbon isotope discrimination (Δ) fell into three categories. The highest Δ, found in lichens comprising a phycobiont plus cyanobacteria limited to pockets in the thallus (known as cephalodia), ranged from 24 to 28‰, equivalent to a carbon isotope ratio (δ13C) of around -32 to-36‰ vs. Pee Dee Belemnite (PDB) standard. Further evidence was consistent with CO2 supply to the carboxylating system entirely mediated by diffusion rather than a CCM, in that thallus CO2 compensation point and online instantaneous Δ were also high, in the range normally associated with C3 higher plants. For lichens consisting of phycobiont or cyanobiont alone, organic material Δ formed two distinct ranges around 15‰ (equivalent to a δ13C of -23%.). Thallus compensation point and instantaneous Δ were lower in the cyanobiont group, which also showed higher maximum rates of net photosynthesis, whether expressed on the basis of thallus dry weight, chlorophyll content or area. These data provide additional evidence for the activity of a CCM in cyanobiont lichens, which only show photosynthetic activity when reactivated with liquid water. Rates of net CO2 uptake were lower in both phycobiont associations, but were relatively constant across a wide working range of thallus water contents, usually in parallel with on-line Δ. The phycobiont response was consistent whether photosynthesis had been reactivated with liquid water or water vapour. The effect of diffusion limitation could generally be seen with a 3–4‰ decrease in instantaneous Δ at the highest water contents. The expression of a CCM in phycobiont algae, although reduced compared with that in cyanobacteria, has already been related to the occurrence of pyrenoids in chloroplasts. In view of the inherent requirement of cyanobacteria for some form of CCM, and the smaller pools of dissolved inorganic carbon (DIC = CO2 + HCO inf3 su− + CO inf3 su2− ) associated with phycobiont lichens, it appears that Δ characteristics provide a good measure of the magnitude of any CCM, albeit tempered by diffusion limitation at the highest thallus water contents.

Microphytobenthos primary production of Tagus estuary intertidal flats (Portugal)

Abstract: The purpose of this study was to measure primary productivity of microphytobenthos of intertidal mudflats of Tagus estuary. Sampling occurred from 1991 to 1992, during low tide of spring waters on 2 stations, each one representative of a typical habitat. Net photosynthesis rates (NP) were measured in undisturbed sediment cores incubated in the laboratory andin situ. The results obtained indicated that NP in the laboratory was similar for the two stations, (mean values of 1.1 and 1.3 mmol O2 m−2 h−1, within a range of 5-fold). A stepwise regression analysis combining biotic and abiotic factors was performed to explain temporal variability, indicating that NP in each site was influenced by different parameters, with the exception of precipitation, which might play an important role in the disruption of sediment-water interface. Photosynthesis-Irradiance curves constructed with the results obtained insitu showed similar photophysiological responses of the two communities. Based on the values of photosynthetic efficiency (α), and of optimal light intensity (lk) measured and on the combination of the photoperiod pattern and the amount of light available for each sampling site, an estimation of total annual productivity is given: 47–178 g C m−2.

Expression patterns of laminin receptor splice variants α6Aβ1 and α6Bβ1 suggest different roles in mouse development

Abstract: The alpha 6 beta 1 integrin is a receptor for laminins and is present from early stages of mouse embryogenesis. In the present study we determined the temporal and spatial expression of the two cytoplasmic splice variants of the alpha 6 integrin subunit, alpha 6A and alpha 6B, in the early- and mid-gestation mouse postimplantation embryo using RT-PCR, in situ hybridization, and immunofluorescence. Our results show that alpha 6B is present in the embryo at all stages studied and is expressed before alpha 6A. alpha 6A expression begins in 8.5 day p.c. embryos and is initially exclusively localized to the developing heart. In 8.5 (and 9.5) day p.c. embryos alpha 6A mRNA and protein are present in a gradient in the myocardium of the heart tube from strongest expression in the sinus venosus and in the common atrial chamber to a weakening expression along the ventricle and bulbus cordis. In 10.5 day p.c. embryos this gradient is less evident and in 12.5 day p.c. embryos alpha 6A mRNA and protein are present in comparable amounts between atria and ventricles. Neither alpha 6A nor alpha 6B is present in endocardial cushion tissue. By day 12.5 p.c. alpha 6A expression is also present in the developing epidermis, dental primordia, lens, gonads, and in a few epithelia such as those of the digestive tract. alpha 6B expression is always much more widespread than alpha 6A expression. For example, only alpha 6B is present in the myotome of the somites of 9.5 day p.c. embryos, in the developing central and peripheral nervous systems, and in the nephrogenic system at all stages studied, except after the differentiation of the gonads when alpha 6A is also present. Furthermore, alpha 6B is the only splice variant present on endothelial cells. We also examined the distribution of the beta 4 integrin subunit to determine whether the alpha 6 beta 4 integrin was present during these stages of development. Beta 4 protein was absent in early postimplantation stages but was present in the epidermis and digestive tract of 12.5 day p.c. embryos. These results show a differential distribution of alpha 6A and alpha 6B during mouse development and thus strongly suggest a different function of these splice variants during embryogenesis. Our results point to a possible role for the alpha 6A beta 1 integrin in the development of the myocardium of the developing heart, but not in the migration of endocardial cushion cells, while alpha 6B beta 1 could be important in the developing nephrogenic and nervous systems.

The biogenesis of the coiled body during early mouse development

Abstract: The coiled body is an ubiquitous nuclear organelle that contains essential components of the pre-mRNA splicing machinery as well as the nucleolar protein fibrillarin. Here we have studied the biogenesis of the coiled body in early mouse embryos. The results show that coiled bodies form and concentrate splicing snRNPs as early as in the maternal and paternal pronuclei of 1-cell embryos. This argues that the coiled body is likely to play a basic role in the nucleus of mammalian cells. In order to correlate the appearance of coiled bodies with the onset of transcriptional activity, embryos were incubated with brominated UTP and the incorporated nucleotide was visualized by fluorescence microscopy. In agreement with previous studies, transcriptional activity was first observed during the 2-cell stage. Thus, coiled bodies form before activation of embryonic gene expression. The appearance of coiled bodies in 1-cell embryos was preceded by the formation of morphologically distinct structures that also contain coilin and which we therefore refer to as pre-coiled bodies. At the electron microscopic level pre-coiled bodies have a compact fibrillar structure, whereas coiled bodies resemble a tangle of coiled threads. Although both pre-coiled bodies and coiled bodies contain the nucleolar protein fibrillarin, the assembly of coiled bodies is separated both in time and in space from ribosome synthesis. Our results suggest that the embryonic ‘nucleolus-like body’ is a structural scaffold that nucleates independently the formation of the coiled body and the assembly of the machinery responsible for ribosome biosynthesis.