Showing papers by "University of Costa Rica published in 1993"
TL;DR: In this article, the Connes-Lott approach to the phenomenological Lagrangian of the standard theory of elementary particles is reviewed in detail and the necessary foundations in noncommutative geometry are fully laid out.
160 citations
TL;DR: Three hemorrhagic factors (BaH1, BH2 and BH3) were isolated from the venom of Bothrops asper by gel filtration on Sephacryl S-200, DEAE-Sepharose chromatography, metal chelate affinity chromatography and hydrophobic interaction Chromatography, indicating a synergism between the three.
82 citations
TL;DR: The results show that these species could be used in agroforestry combinations with different advantages according to the specific objectives desired, whether these are soil protection, nutrient recycling, or enhancement of the growth of associated crops.
Abstract: Litterfall, forest-floor litter biomass and nutrients, short-term litter decomposition and the effects of leaf mulches on initial growth of maize were studied for four indigenous tree species with agroforestry potential:Stryphnodendron microstachyum Poepp. et Endl.(S. excelsum), Vochysia ferruginea Mart,Vochysia guatemalensis Donn. Sm. (V. hondurensis) andHyeronima alchorneoides (O), growing in a young experimental plantation in the Atlantic humid lowlands of Costa Rica. Total annual leaf litterfall was higher inV. ferruginea plots, followed byS. microstachyum, V. guatemalensis andH. alchorneoides; all with values comparable to those reported for other tree species grown in agroforestry combinations in humid tropical regions. Forest-floor litter accumulation was highest underV. ferruginea andV. guatemalensis. Both litterfall and forest-floor litter material had similar patterns in nutrient concentrations: N was higher inS. microstachyum, Ca was higher inV. guatemalensis, K was higher inH. alchorneoides; Mg was higher inV. guatemalensis andH. alchorneoides; H. alchorneoides andV. guatemalensis had the highest P.V. ferruginea litter decomposed more slowly, whileS. microstachyum apparently decomposed faster than the other species. The twoVochysia species showed increases in N and P concentration in decomposing litter after seven weeks in the field,H. alchorneoides showed an increase in litter N and a decrease in litter P, andS. microstachyum showed a net decrease in both N and P over the same time period. The patterns found in the litter bag study were confirmed by results obtained in a tethered-leaves experiment.S. microstachyum andV. ferruginea litters lost more weight when mixed in a 1∶1 proportion than either of them alone. Maize seedlings growing in plots mulched withS. microstachyum andH. alchorneoides leaves showed greatest initial growth, confirming patterns found in decomposition and nutrient release studies. The results show that these species could be used in agroforestry combinations with different advantages according to the specific objectives desired, whether these are soil protection, nutrient recycling, or enhancement of the growth of associated crops.
65 citations
TL;DR: The assay was used for clinical evaluation demonstrating the pre-ovulatory LH surge in two cyclic cows, LH pulsatility in an oophorectomized ewe and LH response to GnRH injection in a boar.
Abstract: A radioimmunoassay for bovine (bLH), ovine (oLH) and porcine (pLH) luteinizing hormone was developed using a human 125 ILH tracer from a commercial kit and a monoclonal antibody (518B7) specific for LH but with low species specificity. Standard curves demonstrated similar binding kinetics when bLH, oLH and pLH were incubated with tracer and antibody for 2 h at room temperature. A 30-min delay in the addition of the tracer gave sufficient sensitivity when analysing pLH. Separation of antibody-bound LH from free hormone was achieved by using second antibody-coated micro Sepharose beads. The assay was validated and the performance compared with that of an RIA currently in use for determination of bLH and oLH (coefficient of correlation: 0.99 and 0.98). Regardless of the standards used, intra-assay coefficients of variation were <10% for LH concentrations exceeding 1 µg/L. The inter-assay coefficients of variation were <15%. The assay was used for clinical evaluation demonstrating the pre-ovulatory LH surge in two cyclic cows, LH pulsatility in an oophorectomized ewe and LH response to GnRH injection in a boar.
57 citations
TL;DR: The nesting biology of a mainly solitary bee,Lasioglossum (Dialictus) figueresi, is compared with that of a possible relative and mainly eusocial bee, L. (D.) aeneiventre, which is active nearly all year round, except during periods of heavy rain.
Abstract: The nesting biology of a mainly solitary bee,Lasioglossum (Dialictus) figueresi, is compared with that of a possible relative and mainly eusocial bee,L. (D.) aeneiventre. These bees nest in the ground in highly disturbed areas in the Meseta Central of Costa Rica. Information is provided on social organization, male production, diel and seasonal activity patterns, pollen utilization, natural enemies and nest architecture.
L. (D.) figueresi nests within aggregations in vertical earthen banks, and 80–90 % of females are solitary during the nest-provisioning phase. Social nests contain two (or rarely three) females which may be either equal or unequal in reproductive status (i.e. mated with developed ovaries or not). Solitary nests and two-female nests do not experience different rates of parasitism. Mid-way through the dry season, females cease provisioning at a time when otherL. (Dialictus) remain active. Females typically remain within their nests, although they occasionally forage for nectar. This behavior is similar of that of “spring gynes” of temperate eusocial species. The egg-to-adult developmental rate ofL. (D.) figueresi is unusually slow for halictine bees, however, so that all the adult females die before their brood eclose in April and May, precluding overlap of generations. The eclosed offspring remain in open cells within their natal nests until mid-June, when both males and females emerge to mate. These newly mated females either establish new nests or re-use old ones.
L. (D.) aeneiventre nests within aggregations in horizontal ground or in vertical banks. A foundress female digs a nest at the beginning of the dry season, although some re-activate old nests. Foundress nests develop into colonies with various kinds of social organization. In contrast toL. (D.) figueresi, L. (D.) aeneiventre is active nearly all year round, except during periods of heavy rain, and produces up to three broods per year. Sweat bees (Hymenoptera: Halictinae) are a socially heterogeneous group of mainly ground-nesting bees which are abundant world-wide. Intra-specific variation in social behavior is prevalent both within and among populations, presumably indicating social and environmental control of behavioral modifications (see e.g. Sakagami and Munakata, 1972; Eickwort, 1986; Packer, 1990; Yanega, 1988; reviewed in Michener, 1990). The initial stages of hymenopteran social evolution are represented by solitary individuals and those in undifferentiated societies, yet their biology is not well known, as is true for the numerous tropical halictine species or populations (see Michener, 1990). The subgenusDialictus ofLasioglossum is a primarily New World group of several hundred species (Moure and Kurd, 1987). These bees are monotonously similar in structure and appearance, yet diverse in social behavior. FemaleLasioglossum (Dialictus) figueresi are usually solitary, and structurally are very similar to their social relativeL. (D.) aeneiventre (Wcislo, 1990 a). The systematic placement of these species with respect to otherL. (Dialictus) is uncertain, but they have no obvious affinities to other recognized species groups (G. C. Eickwort, pers. comm.). Unusual morphological features, such as large size, yellowish wings and pubescence, and features of the genital organs, may indicate thatL. (D.) figueresi is the more derived of the pair, and may therefore be secondarily solitary, as is known for other sweat bees (Packer, 1991).
49 citations
TL;DR: Vipera berus venom displayed in vitro proteolytic, fibrinolytic, anticoagulant, and phospholipase A2 activities, and induced a moderate local myonecrosis, evidenced by histological evaluation of injected tissue and biochemical parameters.
49 citations
TL;DR: Tests of the cytopathogenic effect of MT-III on different cell lines indicated that rat skeletal muscle L6 myoblasts were more sensitive to the toxin than chinese hamster ovary cells, human lung fibroblasts, mouse adrenal tumour cells and rat intestinal epithelial cells.
39 citations
TL;DR: In this paper, the authors analyzed air temperature and wind measurements on the surface and in the free atmosphere taken during the total solar eclipse of July 11, 1991, and found that surface air temperature decreased significantly, 2 to 5 °C in general.
Abstract: Air temperature and wind measurements on the surface and in the free atmosphere taken during the total solar eclipse of July 11, 1991, are analyzed. Surface air temperature decreased significantly, 2 to 5 °C in general, with the lowest values occurring 10 to 30 minutes after totality. In some places, surface wind speed decreased gradually during the eclipse, as a result of the decrease of air temperature and temperature gradients. In other places, it increased due to local atmospheric conditions. A radiosonde launched at 13:26 LT (local time) appeared to have been affected by the moon's shadow at about 13 km height. At this altitude temperature was relatively lower than usual and the balloon carrying the radiosonde experienced an upward acceleration. Also at this altitude wind direction changed and wind speed decreased
39 citations
TL;DR: Inhibition of phospholipase A2 activity, by elimination of calcium and addition of EDTA, resulted in a significant, but not total, reduction in both muscle-damaging and liposomal disrupting effects.
35 citations
TL;DR: During previous studies in patients with isolated proximal renal tubular acidosis (pRTA), the rates of urinary ammonium excretion were considered inappropriately low for their state of chronic metabolic acidosis, suggesting an impaired ability to excrete maximal amounts of ammonium.
Abstract: During previous studies in patients with isolated proximal renal tubular acidosis (pRTA), the rates of urinary ammonium excretion were considered inappropriately low for their state of chronic metabolic acidosis. These observations were made while the patients were on a normal diet as well as when they were undergoing a short ammonium chloride test. Because these findings suggested an impaired ability to excrete maximal amounts of ammonium, the response to the 3-day acid loading test was evaluated in eight patients with isolated pRTA and in 10 normal control subjects. Plasma creatinine, acid-base, and electrolyte values were analyzed before and after 3 days of ingesting 2 mmol/kg.24 h of ammonium chloride. Twenty-four-hour urine specimens were collected the day before and on the third day of acid loading to determine urine pH, as well as the rate of excretion of NH4+ and titratable acid in milliequivalents per 24 h per 1.73 m2. During the basal state, all patients with pRTA had hyperchloremic metabolic acidosis and they excreted urine of lower pH (5.51 +/- 0.18 versus 6.00 +/- 0.13; P < 0.05) and greater titratable acid (29.1 +/- 4.3 versus 21.8 +/- 1.4; P < 0.05); however, they had rates of NH4+ excretion similar to those of controls. On the third day of acid loading, they excreted urine of lower pH (4.66 +/- 0.03 versus 5.00 +/- 0.03; P < 0.05) and equivalent amounts of titratable acid, whereas their NH4+ excretion was significantly less than that of controls (47.7 +/- 4.4 versus 76.3 +/- 5.7; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
32 citations
TL;DR: The MTT-based method described should be useful in the estimation and standardization of anti-myotoxic potency of antivenoms, and in the screening of other neutralizing agents, as a convenient and reliable alternative to the time-consuming quantitative histological methods.
TL;DR: Myotoxic activity, measured by histology and by increment of creatine kinase levels in plasma of mice, was significantly reduced after toxin modification and liposome disruption activity was also significantly lower with the modified toxin.
TL;DR: The immunological reactivity of five crotaline antivenoms for the venoms of ten Costa Rican snakes was determined and there appeared to be no difference in immunogenicity between high-medium mol.
TL;DR: The 4 individual-level factors: cognitive skills reproductive control behavior reproductive experience and contact with family planning programs and the community environment were examined and only actual family size had a significant effect on the probability of a nonnumeric response when the other levels of observations were controlled.
Abstract: Articulo cientifico -- universidad de Costa Rica, Instituto de Investigaciones en Salud.1993. Debido a las politicas de publicacion de la revista no es posible distribuir la version del editor/PDF.
TL;DR: It is proposed that the common presence of NCP in all inclusion bodies implies the existence of a single type of intracellular inclusion body, the different developmental stages of which have previously been considered to be distinct inclusion bodies.
Journal Article•
TL;DR: In this trabajo se identificaron cincuenta y siete especies de cangrejos (anomuros and brachiuros) nuevas for Costa Rica and depositadas in el Museo de Zoologia de la Universidad de Costa Rica as discussed by the authors.
Abstract: En este trabajo se identificaron cincuenta y siete especies de cangrejos (anomuros y brachiuros) nuevas para Costa Rica y depositadas en el Museo de Zoologia de la Universidad de Costa Rica Veinte y cinco de las especies son del Pacifico y 32 del Caribe La extension de la distribucion de 4 de las 25 especies del Pacifico se puede considerar significativa Paguristes praedator, P holmesi, Epialtus sulcirostris y Pilumnus townsendi hasta ahora solo han sido informadas de Mexico y A canthocarpus delsolar; unicamente de Peru Se incluye ademas una lista de las 257 especies informadas para Costa Rica
TL;DR: In Costa Rica, the total solar eclipse of 1991 was measured in several places in Costa Rica as mentioned in this paper, including Puntarenas and Santa Cruz, using a normal incidence pyrheliometer with Schott filters OG530 and RG630.
Abstract: Solar global radiation was measured in several places in Costa Rica during the total solar eclipse that occurred on July 11, 1991. In two of these places, Puntarenas and Santa Cruz, measurements in the ultraviolet range (295–385 nm) were also taken. In Santa Cruz, a normal incidence pyrheliometer with Schott filters OG530 and RG630 was used to measure direct solar radiation in its whole range, and in the 530–2800 nm and 630–2800 wavebands respectively. Global radiation, and consequently direct, diffuse and irradiance in any of the wavebands considered, decreased gradually as the sun was being eclipsed and reached zero during the totality, then increased to their normal values. Data registered in Santa Cruz were used to determine Angstrom's atmospheric turbidity parametersα andβ. Computations show that between 13:00 and 14:30 LT (local time),α decreased andβ increased significantly. This indicates that atmospheric turbidity was high and large particles were more abundant than small ones. The size of hygroscopic particles increased during the eclipse when temperature decreased and relative humidity increased in a comparatively short time.
Journal Article•
TL;DR: The hypothesis that intragastric synthesis of N-nitroso compounds (NOC) in early life could play a role in gastric carcinogenesis was tested by applying the N-Nitrosoproline (NPRO) test to about 50 children living in high- and low-risk areas for stomach cancer in Costa Rica.
Abstract: The hypothesis that intragastric synthesis of N-nitroso compounds (NOC) in early life could play a role in gastric carcinogenesis was tested by applying the N-nitrosoproline (NPRO) test to about 50 children living in high- and low-risk areas for stomach cancer in Costa Rica. The median values of excretion of NPRO and the sum of three nitrosamino acids (micrograms/12 h urine) were 10-20% of those in adults from other geographical high-risk areas for stomach cancer. The urinary NPRO level after proline intake was higher in children from the high-risk area (P < 0.04) and markedly reduced after ingestion of ascorbic acid together with proline (P < 0.05). NPRO levels on the day of proline intake were highly correlated with levels of nitrate excretion (P < 0.001). Mean levels of total NOC in an aqueous (pH 2) extract of cooked beans from the high- and low-risk areas were similar. Acid-catalyzed nitrosation of the extract increased the total NOC concentration up to 1000-fold, but there was no difference between samples from the two areas. About 10% of bean extracts from both areas showed weak direct-acting genotoxicity in Escherichia coli; after acid-catalyzed nitrosation, all samples were genotoxic at similar levels. The diet of children in the low-risk area satisfied recommended levels of intake of energy and most nutrients except riboflavin and retinol equivalents. Diets from the high-risk area were deficient in energy intake and all nutrients except protein and vitamin C.(ABSTRACT TRUNCATED AT 250 WORDS)
Journal Article•
TL;DR: La mezcla racial- incluye ge nes negroides y caucasoides en distintas frecuencias (1-30%) dependiendo del contexto ecologico y cultural de las tribus.
Abstract: Se ahillizo la diversidad genetica de 9 tribus amerindias (boruca: bokota, bribri, cabecar, guatuso, guaymi, huetar, kuna y teribe) de - Costa Rica y Panama, utilizando un total de 48 loci que incluyen sistemas enziinaticOs, grupos sanguineos y proteinas del suero. La heterocigosis media (H) y la frecuencia de polimorfismos son relativamente bajas (H=O.OSS; P=0.217). La diferenciacion genetica dentro de tribus es baja con excepcion del cabecar (Gst=O.Q49), pero es alta entre las. distintas tribus (Gst=O.073). La mezcla racial- incluye ge nes negroides y caucasoides en distintas frecuencias (1-30%) dependiendo del contexto ecologico y cultural de las tribus. Se considera que factores como los sistemas de parentesco y la deriva genetica al azar explican en parte estos resultados. De manera general la diversidad genetica de estas tribus chibchas es similar a otras de Suramerica con diferentes lenguajes.
TL;DR: The clotting enzyme (Stenoxobin), from the venom of Lachesis muta stenophyrs, was purified by gel chromatography on Bio-gel P-100 followed by agmatine CH-Sepharose-4B and FPLC on Mono Q column and Amino acid analysis revealed a low content of tryptophan and a high content of acid residues.
TL;DR: In this article, the Taylor asymptotic expansion of a perturbed distribution of the form is presented, where a smooth function is defined in Ω n. The authors present the one-dimensional theory to illustrate the underlying concepts and then discuss the multi-dimensional case.
Abstract: We present the Taylor asymptotic expansion of a perturbed distribution of the form
is a smooth function defined in ℝn. First we present the one-dimensional theory to illustrate the underlying concepts and then we discuss the multi-dimensional case. We find that various known results follow as special limits of our results.
TL;DR: The leafhopper tribe Scaphytopiini is reviewed, and a key to genera given and its characters discussed.
Abstract: The leafhopper tribe Scaphytopiini is reviewed, and a key to genera given. The following taxonomic changes are made: Masiripius lugubris (Distant) comb. nov. (from Mahalana); Mahalana Distant, junior synonym of Platymetopius Burmeister syn. nov. (Athysanini); Hododoecus bunyensis Evans comb. nov. (from Stenometopius) (Stenometopiini). In addition, the monotypic genus Nesothamnus Linnavuori is transferred from Athysanini to Scaphytopiini and its characters discussed.
TL;DR: The finding suggests that turbidity in equine antivenoms depends on the interaction of at least three factors: (a) freezing, (b) high initial cholesterol and lipoprotein concentration in the serum, and (c) addition of phenol during fractionation of serum.
TL;DR: Two myotoxins isolated from B. asper ( myotoxin II) and B. nummifer (myotoxin I) snake venoms have been crystallized and their diffraction properties are described.
TL;DR: In this article, a matrix transformer constructed from integrated core and z-folded flex circuits is described and the magnetizing inductance is derived using the reluctance method and exploiting structural periodicity and symmetry.
Abstract: Winding and core geometries are described for a matrix transformer constructed from integrated core and z-folded flex circuits. The magnetizing inductance is derived using the reluctance method and exploiting structural periodicity and symmetry. The internal leakage inductance is computed from the magnetic field distribution, and the interconnect leakage inductance from inductance formulas and current distribution. The results show that the interconnects are responsible for most of the leakage inductance. The modeling predicts inductance values that agree well with experimental measurements. >
TL;DR: In this article, ground measurements of the geomagnetic field, during the total solar eclipse of July 11, 1991, were carried out at three sites in Costa Rica located within the eclipse's path of totality.
Abstract: Ground measurements of the geomagnetic field, during the total solar eclipse of July 11, 1991, were carried out at three sites in Costa Rica located within the eclipse's path of totality. Near totality, there was a significant change in the total intensity,F. Its normal decrease in the afternoon hours was interrupted during a period of about 45 min, in whichF varied very little. This was due mainly to a small variation in horizontal intensity,H, during such a period. The departure ofF from normal lasted about 100 min; its maximum departure was near 10 nT and occurred about 38 min after totality, The declination,D, also experienced a small change (about 2.3 min) during the total period of the eclipse. The vertical intensity,Z, and the inclination,I, did not show significant changes.
TL;DR: It is concluded that pediatric primary-care providers in rural Mexico possess a baseline level of knowledge about otitis media that can be significantly enhanced with one educational session, and this teaching effort produces an impact on practice pattern that lasts at least 2 years.
Abstract: The World Health Organization has designated the teaching of otitis media management skills a “priority” status. Effective treatment of ear disease requires that the physician be both informational...
TL;DR: A T-matrix formalism is used to calculate local electric fields around clusters of prolate spheroids in the long-wavelength regime and the observed red shifts in the resonant wavelengths of the characteristic peaks are shown to obey an exponential relationship as a function of interparticle separation.
Abstract: A T-matrix formalism is used to calculate local electric fields around clusters of prolate spheroids in the long-wavelength regime. The calculations are performed as a function of interparticle distance as well as angle of orientation. The observed red shifts in the resonant wavelengths of the characteristic peaks are shown to obey an exponential relationship as a function of interparticle separation and a sinusoidal relationship as a function of angle of rotation of the spheroid. The behavior of the cluster is discussed and the two effects of separation and rotation are compared.
TL;DR: In this article, the authors reviewed basic housing conditions in Costa Rica during the 1980s and described the National Housing Programme implemented under the Arias administration (1986-1990) and the National Bamboo Programme, initiated within this framework, as a prototypical approach to using inexpensive local building materials.
TL;DR: Blood inoculation in mice showed that Toxoplasma organisms circulate in blood after 1 h of oocyst infection, and Parasites were detected up to 15 days later and then disappeared from the bloodstream concomitantly with cyst formation in the brain, probably due to antibody presence.
Abstract: Blood inoculation in mice showed that Toxoplasma organisms circulate in blood after 1 h of oocyst infection. Parasites were detected up lo 15 days later and then dissapeared from the bloodstream concomitandy with cyst formation in the brain, probably due to antibody presence. Immunosuppression causedby cortisone acetate treatment induced Toxoplasma bloodstream invasion in chronically infected rnice and hamsters, causing death in some. Natural dissemination is discussed in relarion with congenital toxoplasmosis. Induced immunosuppressive effect is compared with that produced by natural diseases such as Hodgkin, lymphome, AIDS and others.