Showing papers by "University of Córdoba (Spain) published in 1990"

Evaporation Measurements beneath Corn, Cotton, and Sunflower Canopies

Abstract: The purposes of this investigation were to : develop a microlysimeter that would be representative of field conditions for measuring evaporation (E) from soil; separate evaporation and transpiration (T) estimates by concurrent measurements of ET and E from soil on a daily basis under irrigated cotton, corn and sunflower; and assess the interactions between the two ET components under the prevailing experimental conditions

A possible dual mechanism of the anovulatory action of antiprogesterone RU486 in the rat.

Abstract: The purpose of these experiments was to investigate the mechanism of the anovulatory action of antiprogesterone RU486 (RU486) in rats by studying its effects on follicular growth, secretion of gonadotropins and ovarian steroids, and ovulation. Rats with 4-day estrous cycles received injections (s.c.) of either 0.2 ml oil or 0.1, 1, or 5 mg of RU486 at 0800 and 1600 h on metestrus, diestrus, and proestrus. At the same times, they were bled by jugular venipuncture to determine serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), 17 beta-estradiol (E), and progesterone (P). On the morning of the day after proestrus, ovulation and histological features of the ovary were recorded. Rats from each group were killed on each day of ovarian cycle to assess follicular development. Rats treated similarly were decapitated at the time of the ovulatory LH surge and blood was collected to measure LH. The serum levels of LH increased and those of FSH decreased during diestrus in rats treated with RU486. Neither E nor P levels differed among the groups. Treatment with RU486 caused both a blockade of the ovulation and an increase in ovarian weight in a dose-dependent manner. At the time of the autopsy (the expected day of ovulation), rats treated with 1 mg RU486 had ovaries presenting both normal and post-ovulatory follicles and unruptured luteinized follicles. Rats treated with 5 mg RU486 presented post-ovulatory follicles without signs of luteinization. The number of follicles undergoing atresia increased in rats treated with RU486. Rats treated with 5 mg RU486 exhibited a significant decrease in ovulatory LH release. The mechanism by which RU486 produces the ovulatory impairment in rats seems to be dual: first, by inducing inadequate follicular development at the time of the LH surge and second, by reducing the amount of ovulatory LH released. The physiological events-decreased basal FSH secretion and follicular atresia-that result from use of RU486 cannot be elucidated from these experiments and should be investigated further.

Extracellular deamination of L-amino acids by Chlamydomonas reinhardtii cells.

Abstract: When grown in the light and in a Tris-acetate phosphate medium, cells of Chlamydomonas reinhardtii Dang. can use the following l-amino acids as a sole nitrogen source: asparagine, glutamine, arginine, lysine, alanine, valine, leucine, isoleucine, serine, methionine, histidine, and phenylalanine, whereas, in the absence of acetate, the cells only used l-arginine. The utilization system in the acetate medium consisted of an extracellular deaminating activity induced by l-amino acids; it took between 10 to 30 h before the system appeared in cells previously grown with ammonium. This deaminase activity was nonspecific, required an organic carbon source for its de-novo synthesis, and was sensitive to high ammonium concentration and light deprivation.

Predicting phosphate sorption in soils of mediterranean regions

Abstract: Phosphate sorption curves give useful information about the management of the P fertility in soils. This study was conducted to examine how P sorption characteristics were influenced, and could be predicted from the properties of Mediterranean soils of Spain. The 114 soils studied differed widely in origin and properties and were grouped as calcareous (43) and noncalcareous (71). Citrate-bicarbonate-dithionite extractable Fe (Fed) and Al (Ald) and clay were the properties best correlated with the P sorbed and the P buffer capacity at an equilibrium concentration of 0.2 mg P l−1. This suggests that Fe oxides and silicate clays play a significant role in P sorption. Stepwise regression analysis showed, however, that clay was not a significant variable in the calcareous group, but active CaCO3 was. Prediction of the P sorption parameters was better for the noncalcareous than for the calcareous group. This reduced ability to predict P sorption in calcareous soils may be due to the inability of total or active CaCO3 to adequately measure the reactivity of carbonates towards P sorption. From 53 to 75% of the variation in P sorption parameters could be explained by regression equations including all or several of the following routinely-determined soil properties: clay, pH, Fed, and active CaCO3. These equations could, therefore, provide a simple and rapid estimation of P sorption in soils of Mediterranean regions.

Ascorbate Free Radical Stimulates the Growth of a Human Promyelocytic Leukemia Cell Line

Abstract: Ascorbate free radical stimulates the growth of human promyelocytic leukemia cells (HL-60) in the presence of a limited amount of serum (1%) when added to the cells under conditions where it is impermeable. Maximum growth stimulation occurs at concentrations from 5 × 10-9 to 2 × 10-8 m. Ascorbate mimicks the stimulation effect of its free radical but stimulates at higher concentrations. Autoxidation of ascorbate by oxygen produces its free radical, which apparently causes growth stimulation. Ascorbate could be regenerated by intact cells in vitro , since prevention of autoxidation of ascorbate in the presence of cells is observed. Neither dehydroascorbate nor isoascorbate increases HL-60 cell growth. Short term incubation of cells in the presence of ascorbate free radical induced intracellular NADH oxidation. We propose that the stimulation of growth of HL-60 cells shown here could be caused by activation of the transplasma membrane electron transport system by the ascorbate free radical.

Changes in the expression of HLA-class II antigens on peripheral blood monocytes from aged humans.

Abstract: Increased incidence of infections, cancer, monoclonal gammopathies and rheumatic diseases in aged humans has been described. Histocompatibility antigens are involved in the regulation of immune response and it has been suggested that age-related alterations in the murine immune system may be due to changes in the expression of these antigens on the immunocompetent cells. In this paper we study the expression of HLA-DR/DP and HLA-DQ antigens on monocytes from healthy human elderly donors. Results show that peripheral blood monocytes from elderly subjects express decreased levels of HLA-DR/DP antigens (61.5 + 16.3) when compared to young controls (82.5 + 8.5) and increased levels of HLA-DQ antigens (40.4 + 16.8 and 23.6 + 7.1, respectively). The abnormal levels of expression of HLA-class II molecules could be related to the altered immune functions observed in elderly people.

Nitrate and nitrite uptake and reduction by intact sunflower plants.

Abstract: Nitrogen-starved sunflower plants (Helianthus annuus L. cv. Peredovic) cannot absorb NO 3 − or NO 2 − upon initial exposure to these anions. Ability of the plants to take up NO 3 − and NO 2 − at high rates from the beginning was induced by a pretreatment with NO 3 − . Nitrite also acted as inducer of the NO 2 − -uptake system. The presence of cycloheximide during NO 3 − -pretreatment prevented the subsequent uptake of NO 3 − and NO 2 − , indicating that both uptake systems are synthesized de novo when plants are exposed to NO 3 − . Cycloheximide also suppressed nitrate-reductase (EC 1.6.6.1) and nitrite-reductase (EC 1.7.7.1) activities in the roots. The sulfhydryl-group reagent N-ethylmaleimide greatly inhibited the uptake of NO 3 − and NO 2 − . Likewise, N-ethylmaleimide promoted in vivo the inactivation of nitrate reductase without affecting nitrite-reductase activity. Rates of NO 3 − and NO 2 − uptake as a function of external anion concentration exhibited saturation kinetics. The calculated Km values for NO 3 − and NO 2 − uptake were 45 and 23 μM, respectively. Rates of NO 3 − uptake were four to six times higher than NO 3 − -reduction rates in roots. In contrast, NO 2 − -uptake rates, found to be very similar to NO 3 − -uptake rates, were much lower (about 30 times) than NO 2 − -reduction rates. Removal of oxygen from the external solution drastically suppressed NO 3 − and NO 2 − uptake without affecting their reduction. Uptake and reduction were also differentially affected by pH. The results demonstrate that uptake of NO 3 − and NO 2 − into sunflower plants is mediated by energy-dependent inducible-transport systems distinguishable from the respective enzymatic reducing systems.

Natural killer susceptibility is independent of HLA class I antigen expression on cell lines obtained from human solid tumors.

Abstract: The susceptibility to natural killer (NK) cell-mediated cytotoxicity of 20 cell lines obtained from human solid tumors and their class I histocompatibility antigen (HLA) levels were studied in an attempt to determine whether major histocompatibility complex (MHC) products expressed on cells derived from human solid tumors influence NK susceptibility. The effect of interferon-gamma (IFN-gamma) treatment on these elements was also analyzed. The MHC class I (HLA-ABC, HLA-A and HLA-B) antigen levels and degree of NK lysis were very heterogeneous and no correlation was found on comparison. After treatment with IFN-gamma a marked decrease in NK susceptibility was observed in all the cell lines, including the control line K-562. However, the level of HLA class I expression was not modified in any of the lines with the exception of the K-562, which increased. In some cell lines the expression of HLA class I-like antigens. CDla, b and c, was also measured before and after IFN treatment; however, no correlation was found between CD1 levels and NK susceptibility. Consequently, from our results it is possible to conclude that HLA class I antigens do not play a decisive role in NK susceptibility of cell lines derived from human solid tumors and to suggest that molecules which are not HLA class I antigens but IFN-gamma inducible may confer NK resistance to these lines.

Life history patterns of the common carp, Cyprinus carpio , in the estuary of the Guadalquivir river in south-west Spain

Abstract: We examined 1567 carp caught in rice field drainage canals in the estuary of the Guadalquivir river (37° N, 6° 25′ W). The stock was comprised of a small number of age groups, among which 0+ and 1+ were dominant. Growth was divided in four periods: rapid (June–July); slow (August–November), no growth (December–March), and resumed growth in April when an annulus was formed. A classification based on 12 wild carp populations revealed that growth depends on latitude, and that growth of the studied stock was mediocre, probably due to high salinity. A decrease in somatic condition coincided with an increase in gonadosomatic index (GSI). Specimens of the same stock, age and/or length showed considerable difference in development of the gonads. Gonadal activity began in September and by late Autumn some gonads had reached up to 20% of body weight. The situation remained static during Winter till April, when most reproduction occurred. Later, GSI values decreased to reach a minimum in September. Maximum average GSI values in females were twice those in males. Both sexes achieved maturity during the third growing season (2+ age-group) at a minimum fork length (F.L.) of 110 mm. Fecundity, before reproduction, was expressed by Fec = 241.701 F.L. (mm) − 26776.2. The sex ratio did not differ significantly from 1 : 1.

Levels of metals in canned meat products : intermetallic correlations

Abstract: The analytical control of heavy metals in food is particularly important, since these pollutants are notably cumulative in nature and, therefore, can be toxic to humans. Their determination in foods of animal origin is of interest. In this study analyses of seven heavy metals in semipreserved ham and shoulder pork, preserved lunch pork and pork liver paste were performed to determine the possible influence of the container itself on the levels of metals in such products. Not only were the toxic elements cadmium and lead studied, but also copper, zinc, iron, nickel and manganese which, although not essentially toxic, could, in high concentration, cause public health hazards or a decrease in the organoleptic quality of the canned product, with resultant economic effect.

Possible role of changes in post-natal gonadotrophin concentrations on permanent impairment of the reproductive system in neonatally oestrogenized male rats

Abstract: Rats were treated neonatally with oestrogen (500 micrograms oestradiol benzoate injected on Day 1 of life). Treatment with FSH and LH (80 micrograms/100 g body wt and 40 micrograms/100 g body wt respectively) during the early post-natal period (Days 1-10) abolished the effects of oestradiol on the morphological and functional development of the testes and on the regulation of prolactin secretion, but had no action on the effects of oestradiol on the development of the sex accessory glands. Treatment with prolactin (100 micrograms/100 g body wt) during the early post-natal period did not affect the integrity of the reproductive system in adult life. These results suggest that neonatal oestradiol acts indirectly, through an inhibition of gonadotrophin secretion on testicular development, and directly on the development of the sex accessory glands.

Differentiation of mast cells during postnatal development of neonatally estrogen-treated rats.

Abstract: The accumulation of mast cells in the testicular interstitium of neonatally estrogen-treated rats was studied from 15 to 90 days of age. The maturation of these cells was assessed by ultrastructural analysis and their histochemical properties were examined with the sequential alcian blue-safranin staining method. The first identifiable mast cells appeared in the testis at 17-20 days of age, as immature cells with proliferative capacity. The density of mast cells increased up to 45 days of age, showing a slight decrease from 45 to 90 days of age. Before 45 days of age, most mast cells showed alcian blue-stained granules, whereas at 45 days of age, most cells presented a mixture of alcian blue and safranin-stained granules. From this age onward, most cells were stained with safranin. These maturational changes were well-correlated with their ultrastructural features. Mast cells presented few and heterogeneous immature granules up to 45 days of age, and many uniform electron-dense granules at 90 days of age. These results indicate that the testicular interstitium of neonatally estrogen-treated rats provides an advantageous environment for the recruitment, proliferation and maturation of connective tissue mast cells.

Use of photochemical reactions in flow injection: determination of oxalate in urine

Abstract: The use of photochemical reactions in flow injection (FI) is reported. The irradiation of an FI reactor with a suitable source facilitates the development of the iron(III)-oxalate reaction, allowing the amperometric determination of the anion in the range 1.0–13.0 µg ml–1, with a relative standard deviation of 1.1% and a sampling frequency of 40 h–1. The proposed method was applied successfully to the determination of oxalate in urine samples.

Type a influenza viruses in birds in southern Spain: Serological survey by enzyme‐linked immunosorbent assay and haemagglutination inhibition tests

Abstract: Summary Of 927 sera taken from poultry from 84 flocks, 33% proved seropositive. Sixty‐three per cent of flocks were found to be seropositive to ELISA (almost all situated within areas where there were waterfowl). The comparable figures, using an HI test, were 16% and 47%, respectively. These data suggest that the influenza A viruses may be enzootic in this area. Of 331 wild birds tested, belonging to 18 species of nine families, 40% proved seropositive to ELISA. Notable high infection rates were found among Anatidae (43%), flamingoes (43%) and sparrows (31%); the latter species may play an important role in carrying the disease from its natural reservoirs to domestic farms. Antibody titres found in wild birds were considerably higher than those found in poultry.

Mutagenesis in Escherichia coli lacking catalase

Abstract: Escherichia coli K-12 strains completely lacking catalase activity due to mutations in katG, katE, and katF genes were constructed in order to assess the role of hydrogen peroxide in mutagenesis. Mutagenesis was monitored by selecting forward mutations to L-arabinose resistance. Lethality was measured at experimental conditions equivalent to those of the mutant yield by using a mixed culture of pairs of isogenic strains distinguished by their differential nutritional requirements. Deficiency in katG, katE, and katF genes leads to an enhanced spontaneous mutation rate as well as an enhanced sensitivity to both the lethal and mutagenic effects of hydrogen peroxide or an H2O2-generating mixture of compounds, such as coffee. To compare further the responses of the catalase-deficient bacteria to those of catalase-proficient counterparts, other genotoxins were analyzed. Both catalase-deficient and catalase-proficient strains were equally mutated by MMS, 4-NQO, and ultraviolet light. It is concluded that the bacterial strains and the mutagenicity tests described in the paper represent a useful tool to study the role of H2O2 in mutagenesis.

Flow Injection Analysis

Abstract: A liquid pump, particularly though not exclusively suitable for use in flow injection analysis, and comprising a reservoir 3 an outlet tube 6 for conducting liquid 2 from the reservoir and a device for introducing gas into the liquid in the reservoir to displace liquid therefrom through the tube. The gas may be introduced in the form of a series of rapid pulses of controlled duration and frequency and is introduced at a fixed level relative to the entrance to the outlet tube.

Differential toxicity of simazine and diuron to torilis arvensis and lolium rigidum

Abstract: Summary: In a soil application, Torilis arvensis was nearly as susceptible as Lolium rigidum to simazine but was 18-fold more tolerant to diuron. Treat ment with diuron inhibited photosynthesis in L. rigidum but had only a limited effect in T. arvensis although chloroplasts isolated from both species displayed similar susceptibility. 14C-diuron degradation in plants was limited, with the formation of conjugates of mono-methyl-diuron in T. arvensis and N-dealkylated derivatives of diuron in L. rigidum. 14C-diuron entered the roots and was translocated throughout the leaves of L. rigidum but was restricted to stems, leaf petioles and leaf veins of T. arvensis. This difference in transport pattern is proposed to explain the tolerance of T. arvensis to diuron. Resume: Des tests biologiques montrent que Torilis arvensis est presque aussi sensible a la simazinemais 18-fois plus tolerant au diuron que Lolium rigidum. Un traitement au diuron bloque la photosynthese dans les feuilles de L. rigidum mais a peu d'effet dans celles de T. arvensis bien que les chloroplastes isoles des deux especes aient une sensibilite voisine. La degradation de l'herbicide dans les plantes est faible. Chez T. arvensis elle conduit a des conjugues du diuron monomethyle et chez L. rigidum aux derives N-dealkyles du diuron. Le diuron radioactif est bien absorbe par les racines des plantes. Il migre dans les feuilles de L. rigidum mais s'accumule dans les tiges, les petioles et les nervures des feuilles de T. arvensis. Cette difference de transport pourrait expliquer la tolerance de T. arvensis. Zusammenfassung: Bei Bodenapplikation war Torilis arvensis gegenuber Simazin etwa genauso empfindlich wie Lolium rigidum, tolerierte Diuron aber 18mal besser. Diuron verhinderte die Photosynthese bei Lolium rigidum, hatte aber bei Torilis arvensis nur eine beschrankte Wirkung, obwohl isolierte Chloroplasten bei beiden Arten ahnlich empfindlich waren. Der Abbau von 14C-Diuron in den Pflanzen war schwach, bei Torilis arvensis wurden Monomethyl-Diuron-Konjugate gebildet, bei Lolium rigidum N-diealkylierte Derivate. 14C-Diuron wurde uber die Wurzeln aufgenommen und von Lolium rigidum in die Blatter vollstandig transloziert, von Torilis arvensis aber nur in den Stengel, die Blattstiele und -nerven. Dieser Unterschied im Transportverhalten wurde zur Erklarung der Toleranz von Torilis arvensis gegenuber Diuron herangezogen.