Showing papers by "University of Extremadura published in 1992"

Haloperidol disposition is dependent on the debrisoquine hydroxylation phenotype: increased plasma levels of the reduced metabolite in poor metabolizers.

Abstract: We have previously shown that the disposition of haloperidol is decreased in poor (PM) compared to extensive (EM) metabolizers of debrisoquine. We now report that the plasma levels of the reduced metabolite of haloperidol, after a single 2- or 4-mg oral dose of the parent drug, are significantly higher in PM than in EM of debrisoquine. As PM have higher concentrations of haloperidol than EM, more of the reduced metabolite should be formed, since the formation of reduced haloperidol from haloperidol seems to be independent of the debrisoquine hydroxylase (cytochrome P4502D6) activity. Another reason to explain the increased metabolite levels in PM may be a decreased reoxidation of the reduced metabolite to haloperidol, as this reaction is catalyzed by cytochrome P4502D6. A third reason might be that reduced haloperidol is transformed to other metabolites by this enzyme.

Stable constant mean curvature tori and the isoperimetric problem in three space forms

Abstract: Introduction Let ψ : M → N be an immersion of an orientable surface into a three dimensional oriented Riemannian manifold. Then ψ has constant mean curvature if and only if it is a critical point of the area functional for any compactly supported variation that preserves the volume enclosed by the surface. In this context we say that the constant mean curvature immersion ψ is stable if the second variation formula of the area, which we call henceforth the index form of ψ, is non negative for all variations of the above type. Otherwise, ψ is stable if for any f ∈ C∞(M) with compact support such that ∫ M f dA = 0, we have

Spherical and rod-like zinc oxide microcrystals: morphological characterization and microstructural evolution with temperature

Abstract: Spherical ZnO microcrystals obtained by spray pyrolysis and thermal decomposition methods as well as rod-like ZnO particles (prismatic and needle shaped) prepared from precipitation in aqueous solutions, have been characterized by electron microscopy, X-ray diffraction and infrared spectroscopy. Very different sizes of ZnO particles were obtained from spray pyrolysis. However, only the larger particles (0.7 μm) were found to be slightly deformed by infrared spectroscopy. From thermal decomposition of zinc acetate, fine particles of average size 0.05 μm, rather spherical and agglomeration free were obtained. The role of initial size and morphology in the thermal evolution is fundamental: very fine spherical particles (0.01–0.02 μm), can be sintered to give particles of 0.1–0.3 μm at 875 °C with unchanged morphology. When the temperature induces a change in spherical shape, the first microstructural changes appear to take place through the crystallographic c-axis. However, for rod-like particles, changes begin from the a, b axes, being faster for needle-shaped microcrystals.

Molecular characterization of a Leishmania donovani infantum antigen identified as histone H2A.

Abstract: A Leishmania donovani infantum promastigote cDNA expression library was screened with a serum obtained from a dog naturally infected with this parasite. One of the positive clones obtained revealed nucleotide sequence similarities with the histone H2A genes from various organisms. Northern blot analyses and sequence data of three independently isolated cDNA clones indicated that the Leishmania H2A mRNAs are polyadenylated, as are the basal histone mRNAs of higher eukaryotes and the histone mRNAs of yeast. The analysis of the genomic distribution of the DNA coding for histone H2A suggested that, in L. d. infantum, there are at least four genes coding for the H2A protein. It is likely that there is a simultaneous expression of at least two of the H2A genes since differences in nucleotide sequence between two of the sequenced cDNAs were observed. Affinity-purified antibodies against the β-galactosidase-fused H2A protein recognize specifically a Leishmania protein band with a molecular mass of 14 kDa.

Lower Cambrian acritarchs from northern Spain: the Precambrian-Cambrian boundary and biostratigraphic implications

Abstract: Acritarchs are reported from basal Cambrian rock units inthe Cantabrian region of northern Spain that are known to contain archaeocyathan and trilobite faunas. Biostratigraphic correlation of the Iberian sequences with other regions has been hampered by the strong provincialism of these faunas. However, this report of evidently cosmopolitan acritarch taxaestablishes the time equivalence of early Cambrian trilobite faunas from Iberia, Baltoscandia and the East European Platform (EEP). Our data suggest that the detrital deposition of the Lower Cambrian Herreria Formation embraces at least three (and possibly four) Lower Cambrian acritarch zones previously identified in the EEP, eastern Siberia, Baltoscandia, Scotland, Greenland, Svalbard and western North America. The early Cambrian transgression in northern Spain was probably initiated in Talsy times (Schmidtiellus mickwitzi trilobite Zone in Baltoscandia and the EEP), in part corresponding to the Dokidocyathus regularis archaeocyathian Zone of the Middle Tommotian in Siberia.

Stimulation of the phagocytic function in guinea pig peritoneal macrophages by physical activity stress.

Abstract: A study was made of all the different stages of the phagocytic function in peritoneal macrophages from male guinea pigs [3 (SD 1) months old] before, immediately after, and 24 h after being subjected to stress from physical activity (swimming until exhaustion). The early (10 min) and late (40 min) adherence to tissue substrates, chemotaxis, attachment and phagocytosis of Candida albicans, ingestion of inert particles (latex beads), and basal oxidative metabolism [measured by nitroblue tetrazolium (NBT) reduction] were significantly stimulated by the physical activity. After 24 h, late adherence, attachment capacities, and basal oxidative metabolism returned to basal values, whereas early adherence, chemotaxis, phagocytosis of cells and inert particles, and microbicidal capacity (production of superoxide anion measured by NBT reduction in presence of ingested material) remained significantly increased. The stress produced by physical activity, reflected in increased serum corticosterone values, led to a global stimulation of the phagocytic function.

“Cubication” of non-linear oscillators using the principle of harmonic balance

Abstract: A new method is given of “cubication” of autonomous non-linear oscillators (NLO) of the class ẍ + c1x + c3x3+ ϵ[g(x)+ tf(x)ẍ] i.e.of constructing the cubic oscillator ẍ + λ∗ẍ + c1∗x + c3∗x3= 0 from the NLO. The solution, limit cycles, bifurcations, fixed points, and stability of this NLO are approached by studying its associated cubic oscillator which is equal at least in the largest harmonics (principle of harmonic balance) and by assuming as a first approximation a solution for the NLO problem in terms of Jacobian elliptic functions. When c3= 0, the elliptic functions become circular functions and the present method reduces to the well-studied harmonic-balance method of linearization. The present method is equivalent to a third-order Chebyshev expansion of the NLO force if this is conservative. For a dissipative NLO, it gives the position and features of limit cycles and bifurcations.

Arginine catabolism in the phototrophic bacterium Rhodobacter capsulatus E1F1. Purification and properties of arginase.

Abstract: The phototrophic bacterium Rhodobacter capsulatus E1F1 grew with L-arginine or L-homoarginine as nitrogen source under light/anaerobiosis. However, when L-arginine was used as the only source of both carbon and nitrogen, the bacterium exhibited weak growth levels and the excess of nitrogen was excreted to the medium as ammonia. By contrast, L-ornithine was used under phototrophic conditions as either nitrogen or carbon source. Other compounds of the arginine catabolic pathways, such as putrescine or proline, also supported phototrophic growth of this bacterium. Under heterotrophic/dark conditions, R. capsulatus always showed a low growth rate with those nitrogen compounds. Cells growing on media containing L-arginine, L-homoarginine or L-ornithine induced an Mn(2+)-dependent arginase activity regardless of the presence of ammonium ions and other readily utilizable nitrogen sources. Arginase activity was strongly inhibited by Zn2+, Cu2+, borate, L-cysteine, L-ornithine and gamma-guanidinobutyrate. Mercurials also inactivated arginase, the activity being partially restored by the presence of thiols. Arginase was purified to electrophoretic homogeneity and found to consist of four identical subunits of 31 kDa. The molecular parameters and kinetic constants of arginase from R. capsulatus E1F1 resembled those previously described for the Saccharomyces cerevisiae enzyme rather than those of bacterial arginases.

Histomorphometric analysis of the rumen of sheep during development.

Abstract: Histomorphometric and scanning electron microscopic analyses were performed on 74 embryos and fetuses and 20 sheep (early postnatal to adult age). Histologic differentiation of the omasum took place at 33 days of fetal life, with the appearance of first-order laminae. Second-, third-, and fourth-order laminae appeared at 39, 50, and 59 days, respectively. Neutral mucopolysaccharides first appeared in epithelial cells at 46 days of fetal life, decreasing quantitatively until birth, before subsequently stabilizing in postnatal life. Acid mucopolysaccharides, mucins, and mucoid compounds were not detected. Growth curves and formulas were constructed for each tissue layer. Initial tests involved multiplicative (y = axb), exponential (y = EXP [a + bx]), linear (y = a + bx), and polynomial models (y = a + bx + cx2 + dx3).

Focal dystonia secondary to cavernous angioma of the basal ganglia: case report and review of the literature.

Abstract: The case of a young woman with focal dystonia of the hand due to a cavernous angioma of the basal ganglia is presented. The lesion involved the anterior third of the lentiform nucleus and a large portion of white matter anterior to this nucleus and lateral to the head of the caudate, as shown by magnetic resonance imaging; it was completely removed through a computed tomography-assisted stereotactic craniotomy by microsurgical technique, resulting in the cure of the patient. These facts support the pathophysiological hypothesis of a disruption of the striatopallidothalamic projection to the premotor cortex as the cause of symptomatic dystonia. A review of the reported cases of cavernous angiomas of the deep cerebral gray nuclei shows that this is the first case of cavernous angioma associated with movement disorder.

Circadian rhythms in glutathione and glutathione-S transferase activity of rat liver.

Abstract: The experiments were conduced to examine the existence of circadian rhythms in glutathione concentration and glutathione S-transferase activity in the liver of the rat. In animals synchronized to a 12:12 h light-dark cycle and fasted at 6 different time points to allow exactly 24 h of fasting, both, glutathione concentration and glutathione S-transferase activity show diurnal variation with a maximum during the light period and a minimum at night. On the other hand the hepatic protein level was maximal during the light period and decreased to its lowest level during the dark period. The implications of such oscillations in the circadian rhuthms of toxicological or therapeutical effects of many xenobiotic agents are clear.

Phagocytosis of latex beads by alveolar macrophages from mice exposed to cigarette smoke.

Abstract: Cigarette smoking is known to alter the numerical presence and function of alveolar macrophages. It has been speculated that these cigarette-smoke-induced alterations contribute to the depressed pulmonary defence mechanism commonly demonstrated in smokers. Studies of the phagocytic and bactericidal activities of alveolar macrophages from smokers and non-smokers have yielded conflicting results. The purpose of this study was to investigate the phagocytic capacity of alveolar macrophages from mice exposed to cigarette smoke in relation to the ability to ingest inert particles (latex beads). Measurements were made before (basal values), immediately after, and 1, 12 or 24 h after exposure. Significant decreases were observed in the number of latex beads ingested by 100 macrophages (phagocytic index) and in the phagocytic efficiency for ingesting latex (mean number of latex beads ingested per activated macrophage) immediately after and 1 h after exposure, and in the number of activated macrophages (those with phagocytic activity) immediately after exposure.

Changes in sex hormone binding globulin, high density lipoprotein cholesterol and plasma lipids in male cyclists during training and competition.

Abstract: This study was performed on 13 professional race-cyclists to examine changes in sex hormone binding globulin (SHBG), high density lipoprotein cholesterol (HDL-C) and serum lipid concentrations after training and after competition. While SHBG, total cholesterol and phospholipids increased and free fatty acids (FFA) decreased significantly during training, HDL-C and FFA increased and SHBG and triglycerides (TG) decreased significantly during the competition period. These latter changes in serum lipids and lipoproteins were assumed to be a direct effect of utilisation of muscle and plasma TG as fuels for exertion occurring only in extreme exercise. Changes in SHBG concentrations indicated that they were dependent on the conditions of the physical effort and could be related not only to the concentrations of androgens but also to the reduction in body mass.

Correlation and solvation effects IV.: A systematic analysis of the influence of the cavity size and shape on solvation properties in the polarizable continuum model with electron correlation

Abstract: From the standpoint of models that use a polarizable continuum to represent the solvent in studying the phenomenon of solvation, a systematic and detailed analysis is made of the influence of the cavity size and shape on calculated energies. The solute is represented by its ab initio wavefunction, and the electronic part of the solvation energy is calculated including terms that take into account electron correlation up to third order. The analysis shows the convenience of modeling the cavity according to considerations of homogeneity, which are based fundamentally on how the solute wavefunction is constructed, i.e., the basis set used.

Lead determination in wine by potentiometric stripping analysis

Abstract: Computerized potentiometric stripping analysis (PSA) was used for lead determination in wine samples. In this method sample preparation before determination is limited to dilution with an appropriate supporting electrolyte (0.5 mol/l HCl and 40 mg/l Hg2+). Due to the very high sensitivity, the time needed for one determination can be reduced to 2 min. The method was tested by lead determination in different wines, different concentration ranges and in one European interlaboratory comparison organized by BCR. Using PSA it is possible to simultaneously determine cadmium, lead and copper in wine. For other elements such as Bi, Tl, Hg, Sn, As, Zn the determination procedures are under development. The PSA equipment is available on the market, small in size, relatively cheap and it does not require any special installation such as gas or cooling water.

Absorption of intralipid and interferences from nutrients infused into the peritoneal cavity of the rat

Abstract: We studied the peritoneal absorption and elimination of Intralipid after its intraperitoneal and intravenous infusion into rats, by means of a two-compartment model. Follow-up measurements of the plasma triglyceride rate were made. The peritoneal absorption of Intralipid gives the following absorption and elimination constants: K a (absorption constant from the peritoneal cavity) is 0.106±0.08 h −1 ; K e (elimination constant from the blood stream) is 0.0440±08 h −1 ; and BA a (absolute bioavailability) is 84.5±0.08% 8 hours after infusion. These results show that the intraperitoneal absorption of Intralipid is high and progressive during the first 8 hours, thus supplying the daily caloric needs of the animal through the administration of a single bolus administration, and the plasma triglyceride clearance is faster than the intraperitoneal absorption after the first 6 hours, thus avoiding dangerous overloads. We also studied the behavior of different combinations of glucose, amino acids, and fats infused into the peritoneal cavity of rats in order to observe possible interferences with the absorption of these nutrients. Two microcuries of radioactive L-glucosel-I-C 14 with 5 mL of 5% D-glucose, with 5 mL of 3.5% amino-acid solution, or with 5 mL of 20% fat emulsion were infused intraperitoneally into three different groups of animals. Slight differences of plasma radioactivity were registered among these three groups I hour after infusion. Likewise, small differences of plasma radioactivity were observed between the animals receiving an infusion of 1 μCi of five L-amino-acids-U-C 14 diluted with 5 mL of 3.5% amino-acid solution, with 5 mL of 5% glucose solution, or with 5 mL of 20% fat emulsion 4 and 6 hours after infusion. No differences in the plasma triglyceride rates were observed between those groups of animals infused with 5 mL of 20% Intralipid plus 5 mL of glucose solution or with 20% Intralipid plus 3.5% amino-acid solution compared with the group receiving only 5 mL of 20% Intralipid. The infusion of fats does not seem to interfere with that of other substrates, possibly because of the different absorption route (lymphatic for fats and capillary vessels for amino acids and glucose solutions), but further research is needed to reach conclusive results. Perhaps the prolonged administration of fat, together with other substrates, produces precipitates and other galenic problems that hinder absorptive mechanisms of the preparations.

Oligosaccharide structures of the major exoglucanase secreted by Saccharomyces cerevisiae.

Abstract: We have determined the structures of the N-linked carbohydrate chains, released by endo H, of exoglucanase II that are secreted by wild-type Saccharomyces cerevisiae and by the mnn1 mnn9 and mnn1 glycosylation mutants. The mnn9 mutation does not significantly affect N-linked oligosaccharides of exoglucanase II since we found almost identical structures in both mutant strains consisting of a slightly enlarged core with the basic structure shown in A (where M = mannose). Most of the molecules (77%) were phosphorylated on one of the starred mannoses (34%) or on both (43%) with a diesterified (alpha M-->P-->) or monoesterified phosphate group. In addition, some of the molecules apparently escape normal processing and retain the alpha-(1-->2)-linked mannose (italicized) and/or the three glucoses that are characteristic of the lipid-linked precursor (structure B). In the wild type, we found the same basic structure but more [formula; see text] than 90% of the molecules were modified with one to four alpha-(1-->3)-linked mannoses, which were absent in the strains bearing the mnn1 mutation (structure C). The proportion of acidic components was similar to that found in the mutants (78%), although, in this case, the monophosphorylated forms were more abundant (50%) than the diphosphorylated ones (28%). Most of the phosphate groups (69%) were diesterified by a disaccharide (alpha M-->3 alpha M-->P-->) instead of the single mannose found when the mnn1 mutation was present. In both mnn1 and wild type 10-15% of the oligosaccharides had an extra alpha-(1-->6)-linked mannose in the outer chain, a structure described in the recently isolated vrg1 mutant [Ballou, L., Hitzeman, R.A., Lewis, M. S., & Ballou, C. E. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 3209-3212].

In vitro studies of activities of some antifungal agents against Candida albicans ATCC 10231 by the turbidimetric method.

Abstract: Different criteria (the drug concentration which inhibited 50% of growth [IC1/2], the lowest drug concentration at which growth was just less than 30% of that in a positive control well [IC30], the visual inhibitory concentration [ICv], and the minimum fungicidal concentration [MFC]) were applied to study the effects of some antifungal agents against Candida albicans. Amphotericin B, flucytosine, and bifonazole produced total growth inhibition. Clotrimazole, itraconazole, ketoconazole, and miconazole produced partial growth inhibition. The values of IC1/2 and IC30 were similar for all agents and avoided the problems of partial inhibition; the values of ICv and MFC were higher than those of IC1/2 and IC30.

Matrix-element calculations for hydrogenlike atoms.

Abstract: The method of factorization, together with the hypervirial theorem, is shown to be appropriate for calculating matrix elements of operators that are functions of r, between hydrogenic radial wave functions that may belong to different atoms. Some numerical results are tabulated for matrix elements of the form 〈n'l'\ensuremath{\Vert}${\mathit{r}}^{\mathit{k}}$\ensuremath{\Vert}nl〉. The expressions given are valid for both diagonal- and off-diagonal matrix-element calculations with no limitation on the values of the n and l quantum number or in the power of the operator, which can have either positive or negative values.