Showing papers by "University of Barcelona published in 1985"

Power of the likelihood ratio test in covariance structure analysis

Abstract: A procedure for computing the power of the likelihood ratio test used in the context of covariance structure analysis is derived. The procedure uses statistics associated with the standard output of the computer programs commonly used and assumes that a specific alternative value of the parameter vector is specified. Using the noncentral Chi-square distribution, the power of the test is approximated by the asymptotic one for a sequence of local alternatives. The procedure is illustrated by an example. A Monte Carlo experiment also shows how good the approximation is for a specific case.

Object representation by means of nonminimal division quadtrees and octrees

Abstract: Quadtree representation of two-dimensional objects is performed with a tree that describes the recursive subdivision of the more complex parts of a picture until the desired resolution is reached. At the end, all the leaves of the tree are square cells that lie completely inside or outside the object. There are two great disadvantages in the use of quadtrees as a representation scheme for objects in geometric modeling system: The amount of memory required for polygonal objects is too great, and it is difficult to recompute the boundary representation of the object after some Boolean operations have been performed. In the present paper a new class of quadtrees, in which nodes may contain zero or one edge, is introduced. By using these quadtrees, storage requirements are reduced and it is possible to obtain the exact backward conversion to boundary representation. Algorithms for the generation of the quadtree, Boolean operations, and recomputation of the boundary representation are presented, and their complexities in time and space are discussed. Three-dimensional algorithms working on octrees are also presented. Their use in the geometric modeling of three-dimensional polyhedral objects is discussed.

A Randomized Trial on the Effect of Tubing Changes on Hub Contamination and Catheter Sepsis during Parenteral Nutrition

Abstract: In previous studies the contamination of the catheter hub was found to be a common portal of entry for bacteria causing catheter-related sepsis. Since hub manipulations during tubing changes may increase the risk of contamination, a prospective trial was conducted to find out the effects of the frequency of tubing replacements on hub colonization and catheter sepsis rates. The results were compared with those obtained during an outbreak of coagulase negative staphylococci septicemia. Fifty-two patients were randomly allocated into two groups. Group A (n = 20) had the line changes every 2 days while group B (n = 32) had it replaced every 4 days. When the catheter was removed, the catheter tip and the hub were cultured by a quantitative method. Sterile, colonized, or infected hubs were equally distributed in both groups (A: 80, 15, and 5% vs B: 84, 6, and 10%). There were three episodes of catheter sepsis, one in group A and one in group B due to hub infection, and one in group B due to hematogenous seeding of the catheter tip. There were significant (p less than 0.001) differences between the trial and the historic series in respect to rates of hub colonization infection (19 vs 50%) and catheter sepsis (5.7 vs 40%). Delaying tubing changes does not increase catheter sepsis or hub contamination rates and, together with adequate hub protection, has proved to be a valuable factor in controlling an outbreak of catheter sepsis due to the coagulase negative staphylococci.

Brucellar Spondylitis: A Detailed Analysis Based on Current Findings

Abstract: Three hundred thirty-one cases of brucellosis included in a 10-year prospective protocol were reviewed to identify and follow up patients with spondylitis. Of 20 patients (17 male and three female; mean age, 54 years), spondylitis was diagnosed soon after onset of the brucellosis in 15, there were significant systemic symptoms in 17, and blood cultures were positive for Brucella melitensis in 14. The main symptom was vertebral pain. The commonest radiographic changes were narrowing of the disk and epiphysitis. The discrete character of radiographic alterations and negative uptake on bone scanning caused diagnostic delays in three patients. 99mTc bone scans finally became abnormal in all patients, but were not useful for follow-up because low uptake persisted after the clinical status stabilized. Three patients had paravertebral abscesses; in two of them fever and pain persisted despite antibiotic therapy until diagnosis and surgical drainage. Finally, all patients were cured, ten with sequelae. Brucellar spondylitis often had an acute clinical course with bacteremia. Because neither clinical nor radiographic changes one year after onset were significant, long-term follow-up is not considered necessary except when paravertebral abscess is suspected.

Treatment of chronic lymphocytic leukemia in advanced stages. A randomized trial comparing chlorambucil plus prednisone versus cyclophosphamide, vincristine, and prednisone

Abstract: Ninety-six patients with advanced chronic lymphocytic leukemia (CLL) (Stage C; anemia and/or thrombocytopenia of nonimmune origin) were randomized to receive either chlorambucil (CLR) (0.4 mg/kg orally, day 6) plus prednisone (PDN) (60 mg/m2 orally, days 1-5) every 2 weeks or cyclophosphamide (600 mg/m2 intravenously, day 6), vincristine (1 mg/m2 intravenously, day 6) and prednisone (60 mg/m2 orally, days 1-5) (COP) each month for 5 months. Complete remission (CR) was defined as the total disappearance of signs and symptoms related to the disease. Partial remission (PR) was considered to be achieved when, after treatment, the clinical stage changed to a less advanced one. Thirty (59%) responses (8% CR) with CLR plus PDN and 14 (31%, 2% CR) with COP were observed (P less than 0.01). The survival was not significantly different for the two groups. Patients previously treated had a lower number of responses (11/35, 31%) than those with no previous treatment (33/61, 54%) (P less than 0.05). Patients who attained a CR or a good PR had longer survivals (median not reached) than those with a poor PR (median, 25.2 months) or those who did not respond to treatment (median, 11.5 months) (P less than 0.005).

Blocking and Overshadowing between Intra-Maze and Extra-Maze Cues: A Test of the Independence of Locale and Guidance Learning:

Abstract: Rats were trained on an elevated maze where the rewarded alternative was defined either in terms of intra-maze cues (rubber or sandpaper flooring on rewarded and unrewarded arms, regardless of thei

Contact dermatitis in children.

Abstract: 272 children up to the age of 14 years were patch tested during a 10-year period (1982-1991). 101 children (37.1%) gave positive reactions to 1 or more allergens. Of these, 54.4% (57/101), were considered relevant. The main allergens were, in order of frequency: nickel, rubber compounds, mercuric chloride, cobalt salts, thimerosal, benzoyl peroxide and fragrance mix.

Compartmentation and reliability of sampling procedures in organochlorine pollution surveys of cetaceans

Abstract: The study of the effects of chemical pollution on wildlife basically straddles three scientific disciplines: chemistry, ecology and zoology The research chemist must elaborate systems for detecting and precise quantifying of the different compounds found in the tissues of living organisms, and must study those properties of such compounds which explain the basic processes of transfer and accumulation in the ecosystem The ecologist must put this data together with his own knowledge of the dynamic processes which regulates the ecosystem, both on a general level (movements of air and water masses), and on a particular one (trophic chains, migrations, etc) Finally, the zoologist must bring his knowledge to bear on the biology of the species which are to be studied, in order that the results maybe correctly evaluated and not biased by the particular characteristics of the animals sampled (physiological or reproductive state, age, etc)

Occupational dermatoses from cutting oils

Abstract: 230 patients with occupational dermatitis in I ho metallurgic industry were studied with standard patch tests (GEIDC) and an oil series. An occupational and clinical questionnaire survey was carried out, Responses to paraphenylenediamine, chrome, cobalt in the standard series, and benzisothiazolone, triethanolamine, and Grotan BK® were the main positive results.

Study and Cartography of the Benthic Communities of Medes Islands (NE Spain)

Abstract: . A bionomic study and cartography of the benthos of Medes Islands (NE Spanish coast, Catalan Costa Brava) is presented. From 1977 to 1980 the fauna and flora of the meso- and macrobenthos were sampled by a triple sampling procedure: standard, visual and photographic samples were simultaneously taken along underwater transects, yielding 124 punctual inventories, 176 visual inventories and some 1000 photographic “samples”. These, together with the floristic and faunistic study of each algal and invertebrate group, served as the basis for the bionomic survey of the islands' bottoms. In a first approach, the hard substrata of the infra- and circalittoral Stages were studied, along with the Posidonia meadows, and their communities diagrammatically sketched along representative transects. Further work focused on the submarine caves and tunnels of the area, the supra- and mediolittoral communities and the coastal detritic soft bottoms. The bionomic survey of the Medes Islands has emphasized, with minor differences, the basic similarity between the archipelago's benthic communities and those described elsewhere in the Northwestern Mediterranean. The identified communities or groups of communities are the trottoir, the photophilic algae, the sciaphilic algae (precoralligenous), the coralligenous and cave communities on hard substrata, as well as the Posidonia meadow and the coastal detritic community on soft substrata. These have been used as the basic macro-units in the bionomic cartography of the islands, which has been plotted on a 1:2000 map. Their distribution, over a surface area of some 2 km2 and to a depth of up to 60–70 m, follows that of the heterogeneous substrate, its slope and the hydrodynamical and illumination conditions of the area.

The colonization of drosophila subobscura in chile. ii. clines in the chromosomal arrangements.

Abstract: Drosophila subobscura is a Palearctic species that was first detected in the New World in Puerto Montt (Chile) in February 1978. Since that time, it has spread over a broad area and increased in population density. The South American populations exhibit a high level of chromosomal polymorphism: 20 different arrangements exist, distributed among five chromosomes. Chromosomal arrangement heterozygosity varies from 0.55 to 0.61 in the nine populations examined. Incipient clines in the frequencies of the arrangements are appearing; these clines follow the same latitudinal direction as in the Old World. Wing length significantly decreases with latitude, as it does in Europe. The colonization of South America by D. subobscura appears to be a major natural experiment with outcomes that duplicate the distributional patterns-in chromosomal polymorphism and in wing length- observed in the Old World, thereby strongly supporting the adaptive significance of these patterns. The data show a very rapid effect of natural selection promoting genetic differ- entiation among natural populations.

Cell movement in intact and regenerating planarians. Quantitation using chromosomal, nuclear and cytoplasmic markers.

Abstract: One of the tenets of Wolff and Dubois' 'neoblast theory' of planarian regeneration (Wolff & Dubois, 1948) is that blastema is mainly formed by the accumulation of undifferentiated parenchymal cells (neoblasts) that can migrate, if needed, over long distances to the wound. That neoblasts migrate was claimed by these authors after partial X-irradiation, and total X-irradiation and grafting using planarian strains of different pigmentation. From this they suggested that migration of neoblasts is stimulated by the wound and directed towards it. To study the nature and extent of such 'migration' in intact and regenerating organisms, and in order to avoid the flaws of using pigmentation as a marker, we made grafts between sexual and asexual races of Dugesia(S)mediterranea that differ in a chromosomal marker, and between diploid and tetraploid biotypes of Dugesia(S)polychroa that differ in nuclear size. Also, fluorescent latex beads were used as cytoplasmic markers to follow 'migration' of differentiated cells. The hosts were irradiated or non-irradiated intact and regenerating organisms. The results show that: 1) movement of graft cells into host tissues occurs in intact organisms at a rate of approximately equal to 40 micron/day, and that this increases up to approximately equal to 75 micron/day in irradiated hosts; 2) movement of cells occurs evenly in all directions; 3) regeneration does not speed up rate of movement nor drives cells preferentially to the wound; 4) spreading of cells is mainly due to the movement of undifferentiated cells (neoblasts); and 5) higher rates of movement are correlated with higher mitotic indexes. From this, it is concluded that the so-called 'migration' of neoblasts is not a true cell migration but the result of the slow, even and progressive spreading of these cells mainly caused by random movements linked to cell proliferation. The implications of these results for blastema formation and the origin of blastema cells are discussed.

Liver involvement in multiple myeloma.

Abstract: One hundred twenty-eight records of patients with multiple myeloma were reviewed to assess the incidence and manifestations of liver involvement. Histologic study of the liver was available in 21 patients. Diffuse infiltration of the liver by plasma cells was observed in 10 patients, myeloid metaplasia in four, amyloidosis in two, toxic hepatitis in two, and extrahepatic cholestasis secondary to infiltration of the peripancreatic tissue by plasma cells in one. The clinical signs of plasma cell infiltration of the liver consisted of hepatomegaly in seven patients, mild elevation of liver enzymes in five, and portal hypertension in two. Jaundice was only observed in patients with hepatitis or extrahepatic cholestasis. Liver infiltration by plasma cells did not appear to have a major prognostic significance.

Environmental Control of the Mesoscale Distribution of Primary Producers and its Bearing to Primary Production in the Western Mediterranean

Abstract: The Mediterranean has often been called as a small-scale model of an ocean. Indeed it offers the possibility to study selected phenomena in another dimension. Size is important, as it limits the windows of energy input. A larger ocean allows for a wider spectrum of inputs and much higher local intensities. Tides and anticyclonic gyres are not important in our sea. The Mediterranean has properties of its own: It can be considered as a two-layered, inverse estuary opening into the Atlantic; exchange of water with the Atlantic, in each direction is about 70 times the excessive evaporation that drives it. One consequence is the oligotrophy of the Mediterranean. An oligotrophic system is a good reagent to test consequences of fertilization, providing an ideal place for a detailed analysis of control of primary production. The Mediterranean has a unique feature in the winter mixing in the Gulf of Lions that reaches to extraordinary depths. The annual thermal excursion of surface waters is very large; the thermal cycle controls the density of surface waters and the basic features of the annual biological cycle.

Fine structural changes in cryptogenic fibrosing alveolitis and asbestosis

Abstract: Lung biopsies from 17 patients with cryptogenic fibrosing alveolitis of a cellular rather than fibrotic pattern were examined by transmission electron microscopy in the hope that such cases would show features of pathogenetic significance. Further selection was made by choosing minimally affected areas. There was no ultrastructural evidence of immune complex deposition but alveolar epithelial and capillary damage was frequently found (17 and 14 of the 17 cases respectively). Alveolar epithelial injury consisted of patchy necrosis and regenerative hyperplasia. Alveolar capillary injury consisted of cytoplasmic swelling and basement membrane thickening and reduplication. Many of these features have not been emphasized in previous reports and their prominence in early stages of the disease suggest that they may have pathogenetic significance, possible mechanisms of which are discussed. Similar findings identified during the course of this study in 8 asbestos workers suggest that similar pathogenetic mechanisms may operate in asbestosis.

Renal Hemodynamic Abnormalities in Patients with Short Term Insulin-Dependent Diabetes Mellitus: Role of Renal Prostaglandins

Abstract: To determine if renal functional alterations in diabetes mellitus could be related to disturbances of vasoactive systems, renal plasma flow (RPF), glomerular filtration rate (GFR), PRA (basal and stimulated), plasma catecholamine levels, and urinary excretion of prostaglandin E2 (PGE2), 6-keto-PGF1 alpha, and kallikrein were determined in 21 patients with insulin-dependent diabetes mellitus (IDDM) of short duration and 15 normal subjects. In 7 additional patients with IDDM and in 4 normal subjects, the effect of lysine acetylsalicylate (LAS; 450 mg, iv) on GFR and RPF was studied. Patients with IDDM had higher RPF and GFR than normal subjects. Plasma norepinephrine and basal and stimulated PRA were significantly lower in IDDM than in the control group [161 +/- 82 (+/- SD) vs. 243 +/- 114 pg/ml, 0.19 +/- 0.20 vs. 1.15 +/- 0.33 ng/ml X h, and 0.93 +/- 0.82 vs. 2.8 +/- 1.73 ng/ml X h, respectively). No significant differences were found in the urinary excretion of PGE2, 6-keto-PGF1 alpha, and kallikrein in the two groups. LAS administration significantly reduced RPF (from 641 +/- 72 to 535 +/- 38 ml/min X 1.73 m2) and GFR (from 168 +/- 25 to 150 +/- 18 ml/min X 1.73 m2) in patients with IDDM, but not in normal subjects. In IDDM patients, there was a close direct correlation between the percent decrease in RPF and GFR induced by LAS and the baseline values of these parameters. The results suggest that in IDDM, there may be an imbalance between the degree of activation of the renin-angiotensin and sympathetic nervous systems and the renal production of PGs. The observation that LAS administration reduced RPF and GFR in these patients suggests that renal PGs are involved in the renal hyperperfusion of IDDM.

Spin glass behaviour in an antiferromagnetic non-frustrated lattice: Sr2FeNbO6 perovskite

Abstract: From magnetic susceptibility and hysteresis loop measurements on the cubic perovskite Sr2FeNbO6, it is shown that a spin glass transition does exist in this compound which has a non-frustrated lattice, and only antiferromagnetic interactions. This experimental results allows the authors to conclude that lattice frustration is not an essential feature for the spin glass transition in antiferromagnetic insulators. Moreover, it is argued that short-range atomic correlations, which modify the magnetic phase diagrams of the diluted compounds, make this spin glass transition possible.

Short-term toxicity studies of vanadium in rats.

Abstract: Vanadium (in the form of NaVO3) was given in drinking water to groups of 10 male Sprague-Dawley rats over a period of 3 months at concentrations of 0, 5, 10 and 50 ppm. Vanadium accumulated dose-dependently in the kidneys and spleen. Appearance, behaviour, food and water consumption, growth and mortality of the treated rats of all groups were not affected during the 3-month period. Histopathological investigation showed only mild though dose-dependent lesions in kidneys and spleen. The plasma concentrations of urea and uric acid were increased in the highest exposure groups.

Carbon dioxide embolism during laparoscopy and hysteroscopy.

Abstract: Venous carbon dioxide embolism is a rare but potentially lethal complication of laparoscopy. The risk is increased when it is associated with hysteroscopy. A case is presented of a young women undergoing laparoscopy and hysteroscopy for infertility. Cardiovascular collapse and cardiac arrest, associated with a mill-wheel murmur, occurred during hysteroscopy at the time of a change of position. The patient had irreversible brain damage and died a week later. Early diagnosis and prevention of this serious complication are discussed.