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Biomedical subjects

G Blanco

Publications and source records attributed to G Blanco.

At least 55 records · Page 3Linked to original sources
PubMed1999

Habitat, world geographic range, and embryonic development of hosts explain the prevalence of avian hematozoa at small spatial and phylogenetic scales.

The factors explaining interspecific differences in prevalences of blood parasites in birds are poorly known. We simultaneously assessed 20 social, ecological, life history, and sampling-related variables that could influence hemoparasite prevalences among diurnal birds of prey in Spain. Our results show that multiple factors are responsible for the studied host-parasite association. We confirmed for the first time that prevalence is inversely correlated to the embryonic development period, and thus probably to immune performance, even among closely related birds. Macrohabitat features related to vector availability are also important, prevalences being higher in species breeding in forested habitats. Finally, prevalence is positively correlated with the host's world geographic range. We hypothesize that larger geographic ranges offered more opportunities for host-vector-hemoparasite associations to become established. The results from our multivariate analyses differ from those obtained through univariate ones, showing that all potential factors should be assessed jointly when testing any ecological or evolutionary hypothesis dealing with parasites.

Animals↗
PubMed1999

Temporal, spatial and social segregation of red-billed choughs between two types of communal roost: a role for mating and territory acquisition.

We assessed the value of communal roosting for mating and territory acquisition in nonbreeding red-billed choughs, Pyrrhocorax pyrrhocorax. Between 1991 and 1996 we surveyed all communal roosts, breeding territories and vacant nest sites in an area of 250 km2in Los Monegros (northeast Spain), as well as other communal roosts in the surrounding 500 km2from 1987 to 1996. Main roosts were used traditionally and throughout the year and gathered more choughs than subroosts, which were used only during the nonbreeding season. Nonbreeding choughs were socially segregated in these roosts according to their age and breeding prospects. Compared with random potential roost sites, main roosts included more first-year birds and were in areas of higher breeding density. Subroosts were mainly joined by choughs of breeding age (at least 2 years old) whose morphology (males) and body condition (females) were similar to those of established breeders, and were in areas with breeding densities as high as around main roosts but with more available nest sites. Nonbreeding choughs that used main roosts later used subroosts, while the converse was rare. More choughs joining subroosts acquired mates than those joining main roosts. Choughs mostly paired with roostmates but also with widowed territorial breeders. Finally, choughs from subroosts acquired territories closer to the roost than those who mated in main roosts, supporting the hypothesis that subroosts reduce the costs of mating and territory acquisition. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

Combined Assessment of Genetic Variability in Populations of Brown Trout (Salmo trutta L.) Based on Allozymes, Microsatellites, and RAPD Markers.

: Genetic variability within and among four Spanish natural populations of Salmo trutta L. was evaluated on the basis of 25 enzyme loci, 3 microsatellite loci, and 9 randomly amplified polymorphic DNAs (RAPDs). A total of 21 allelic markers were found, 12 of which were reported by microsatellites, whereas enzyme and RAPD accounted only for 6 and 3, respectively. Genetic variation within samples was significantly higher for microsatellites and RAPD than for enzyme loci. Although all methods reported a high degree of allelic heterogeneity among samples, also revealing a high degree of gene diversity, genetic relationships depicted by UPGMA dendrograms closely agreed for all kinds of data. Microsatellite loci appeared to be the most feasible technique when searching for specific alleles for a population or an area, owing to the higher number of allelic variants found.

Journal Article↗
PubMed1999

Oxidative cleavage of premithramycin B is one of the last steps in the biosynthesis of the antitumor drug mithramycin.

BACKGROUND: Mithramycin is a member of the clinically important aureolic acid group of antitumor drugs that interact with GC-rich regions of DNA nonintercalatively. These drugs contain a chromophore aglycon that is derived from condensation of ten acetate units (catalyzed by a type II polyketide synthase). The aglycones are glycosylated at two positions with different chain length deoxyoligosaccharides, which are essential for the antitumor activity. During the early stages of mithramycin biosynthesis, tetracyclic intermediates of the tetracycline-type occur, which must be converted at later stages into the tricyclic glycosylated molecule, presumably through oxidative breakage of the fourth ring. RESULTS: Two intermediates in the mithramycin biosynthetic pathway, 4-demethyl-premithramycinone and premithramycin B, were identified in a mutant lacking the mithramycin glycosyltransferase and methyltransferase genes and in the same mutant complemented with the deleted genes, respectively. Premithramycin B contains five deoxysugars moieties (like mithramycin), but contains a tetracyclic aglycon moiety instead of a tricyclic aglycon. We hypothesized that transcription of mtmOIV (encoding an oxygenase) was impaired in this strain, preventing oxidative breakage of the fourth ring of premithramycin B. Inactivating mtmOIV generated a mithramycin nonproducing mutant that accumulated premithramycin B instead of mithramycin. In vitro assays demonstrated that MtmOIV converted premithramycin B into a tricyclic compound. CONCLUSIONS: In the late stages of mithramycin biosynthesis by Strepyomyces argillaceus, a fully glycosylated tetracyclic tetracycline-like intermediate (premithramycin B) is converted into a tricyclic compound by the oxygenase MtmOIV. This oxygenase inserts an oxygen (Baeyer-Villiger oxidation) and opens the resulting lactone. The following decarboxylation and ketoreduction steps lead to mithramycin. Opening of the fourth ring represents one of the last steps in mithramycin biosynthesis.

Amino Acid Sequence↗
PubMed1999

The ocular complications of periocular laser surgery.

Laser periocular surgery has achieved an increased popularity, especially since recent technical developments in the carbon dioxide and erbium:yttrium-aluminum-garnet lasers. Despite the relative safety of these procedures in experienced hands, postoperative complications affecting the periocular region, and the eye itself, may follow laser surgery. Common complications include persistent erythema, hyper- and hypopigmentation, and hypertrophic scarring. Skin infection (viral, bacterial, or fungal) may also jeopardize the postoperative period after periocular laser treatment. Severe burns, transitory or permanent, lower lid ectropion, and even corneal injuries or ocular perforation are among the most severe hazards. A thorough preoperative evaluation, appropriate training, and a cautious and conservative approach are reinforced to minimize such problems.

Eyelid Diseases↗
PubMed1999

Creation of a fully active, cytosolic form of human type I 3beta-hydroxysteroid dehydrogenase/isomerase by the deletion of a membrane-spanning domain.

Human 3beta-hydroxysteroid dehydrogenase/steroid Delta(5)-Delta(4)-isomerase (3beta-HSD/isomerase) is a bifunctional, single enzyme protein that is membrane-bound in the endoplasmic reticulum (microsomes) and mitochondria of cells in the placenta (type I) and in the adrenals and gonads (type II). Two membrane-binding domains (residues 72-89 and 283-310) have been predicted by analyses of hydrophobicity in the type I and II isoenzymes (90% regional homology). These putative membrane domains were deleted in the cDNA by PCR-based mutagenesis, and the two mutant enzymes were expressed by baculovirus in insect Sf9 cells. Differential centrifugation of the Sf9 cell homogenate containing the 283-310 deletion mutant revealed that 94% of the 3beta-HSD and isomerase activities were in the cell cytosol, 6% of the activities were in the microsomes, and no activity was in the mitochondria. This is the opposite of the subcellular distribution of the wild-type enzyme with 94% of the activities in the microsomes and mitochondria and only 6% activity in the cytosol. The organelle distribution of the 72-89 deletion mutant lies between these two extremes with 72% of the enzyme activity in the cytosol and 28% in the microsomes/mitochondria. The integrity of the subcellular organelle preparations was confirmed by electron microscopy. Western immunoblots confirmed the presence of the 283-310 deletion mutant enzyme and the absence of the wild-type enzyme in the insect cell cytosol. The unpurified, cytosolic 383-310 deletion mutant exhibited 3beta-HSD (22 nmol/min per mg) and isomerase (33 nmol/min per mg) specific activities that were comparable with those of the membrane-bound, wild-type enzyme. The isomerase reaction of the cytosolic 283-311 deletion mutant requires activation by NADH just like the isomerase of the microsomal or mitochondrial wild-type enzyme. In contrast, the 72-89 deletion mutant had low 3beta-HSD and isomerase specific activities that were only 12% of the wild-type levels. This innovative study identifies the 283-310 region as the critical membrane domain of 3beta-HSD/isomerase that can be deleted without compromising enzyme function. The shorter 72-89 region is also a membrane domain, but deletion of this NH(2)-terminal region markedly diminishes the enzyme activities. Purification of the active, cytosolic 283-310 deletion mutant will produce a valuable tool for crystallographic studies that may ultimately determine the tertiary/quaternary structure of this key steroidogenic enzyme.

Amino Acid Sequence↗
PubMed1999

Pruritus ani.

The possible dermatological and proctologic causes, of Pruritus Ani that often, due to its persistence and for its consequent lesions of scratching, becomes a real disease, are analysed. Particular attention is given to therapeutical treatment, describing which hygienic-dietetic rules must be followed and which treatments can be utilised, if the cause of the symptom is known and if it is possible to remove it or not. Moreover, personal experience on 312 patients examined in twelve years is reported.

Adult↗
PubMed1998

A STS content physical and transcription map across the ky, kyphoscoliosis, nonrecombinant region.

The ky mouse mutant exhibits a degenerative muscle disease resulting in chronic deformation of the spinal column. Following a previous report describing the mapping of the ky locus to a small region of mouse chromosome 9 (Skynner et al., 1995, Genomics 25, 207-213), we have now undertaken a positional cloning approach to identify candidate genes for ky. A YAC/BAC contig encompassing the ky locus was constructed comprising 48 YAC clones and 48 newly generated STSs. The results from the combined physical and genetic analyses showed that only two overlapping BAC clones, which together do not exceed 260 kb, span the ky nonrecombinant region. A combination of gene hunting methods on the critical BACs has led to the identification of seven coding fragments, which have been tested for expression. The expression analysis and the position of the coding fragments on the contig suggest their grouping in at least four transcription units. One of these transcription units is expressed exclusively in skeletal muscle, making it a suitable candidate for this muscle defect in the ky mouse.

Animals↗
PubMed1998

Differential regulation of Na,K-ATPase isozymes by protein kinases and arachidonic acid.

While several studies have investigated the regulation of the Na, K-ATPase consisting of the alpha1 and beta1 subunits, there is little evidence that intracellular messengers influence the other Na pump isozymes. We studied the effect of different protein kinases and arachidonic acid on the rat Na,K-ATPase isoforms expressed in Sf-9 insect cells. Our results indicate that PKA, PKC, and PKG are able to differentially modify the function of the Na,K-ATPase isozymes. While PKC activation leads to inhibition of all isozymes, PKA activation stimulates the activity of the Na,K-ATPase alpha3 beta1 and decreases that of the alpha1 beta1 and alpha2 beta1 isozymes. In contrast, activation of PKG diminishes the activity of the alpha1 beta1 and alpha3 beta1 isozymes, without altering that of alpha2 beta1. Treatment of cells with arachidonic acid reduced the activities of all the isozymes. The changes in the catalytic capabilities of the Na pump isozymes elicited by PKA and PKC are reflected by changes in the molecular activity of the Na,K-ATPases. One of the mechanisms by which PKA and PKC affect Na pump isozyme activity is through direct phosphorylation of the alpha subunit. In the insect cells, we found a PKA- and PKC-dependent phosphorylation of the alpha1, alpha2 and alpha3 polypeptides. In conclusion, several intracellular messengers are able to modulate the function of the Na,K-ATPase isozymes and some of them in a specific fashion. Because the Na,K-ATPase isozymes have kinetic properties that are unique, this isozyme-specific regulation may be important in adapting Na pump function to the requirements of each cell.

Animals↗
PubMed1998

Augmentation of lung liquid clearance via adenovirus-mediated transfer of a Na,K-ATPase beta1 subunit gene.

Previous studies have suggested that alveolar Na,K-ATPases play an important role in active Na+ transport and lung edema clearance. We reasoned that overexpression of Na,K-ATPase subunit genes could increase Na,K-ATPase function in lung epithelial cells and edema clearance in rat lungs. To test this hypothesis we produced replication deficient human type 5 adenoviruses containing cDNAs for the rat alpha1 and beta1 Na,K-ATPase subunits (adMRCMValpha1 and adMRCMVbeta1, respectively). As compared to controls, adMRCMVbeta1 increased beta1 subunit expression and Na,K-ATPase function by 2. 5-fold in alveolar type 2 epithelial cells and rat airway epithelial cell monolayers. No change in Na,K-ATPase function was noted after infection with adMRCMValpha1. Rat lungs infected with adMRCMVbeta1, but not adMRCMValpha1, had increased beta1 protein levels and lung liquid clearance 7 d after tracheal instillation. Alveolar epithelial permeability to Na+ and mannitol was mildly increased in animals infected with adMRCMVbeta1 and a similar Escherichia coli lacZ-expressing virus. Our data shows, for the first time, that transfer of the beta1 Na,K-ATPase subunit gene augments Na,K-ATPase function in epithelial cells and liquid clearance in rat lungs. Conceivably, overexpression of Na,K-ATPases could be used as a strategy to augment lung liquid clearance in patients with pulmonary edema.

Adenoviruses, Human↗
PubMed1998

Site-directed mutagenesis identifies amino acid residues associated with the dehydrogenase and isomerase activities of human type I (placental) 3beta-hydroxysteroid dehydrogenase/isomerase.

3beta-hydroxysteroid dehydrogenase/steroid delta5-->4-isomerase (3beta-HSD/isomerase) was expressed by baculovirus in Spodoptera fungiperda (Sf9) insect cells from cDNA sequences encoding human wild-type I (placental) and the human type I mutants - H261R, Y253F and Y253,254F. Western blots of SDS-polyacrylamide gels showed that the baculovirus-infected Sf9 cells expressed the immunoreactive wild-type, H261R, Y253F or Y253,254F protein that co-migrated with purified placental 3beta-HSD/isomerase (monomeric Mr=42,000 Da). The wild-type, H261R and Y253F enzymes were each purified as a single, homogeneous protein from a suspension of the Sf9 cells (5.01). In kinetic studies with purified enzyme, the H261R mutant enzyme had no 3beta-HSD activity, whereas the Km and Vmax values of the isomerase substrate were similar to the values obtained with the wild-type and native enzymes. The Vmax (88 nmol/min/mg) for the conversion of 5-androstene-3,17-dione to androstenedione by the Y253F isomerase activity was 7.0-fold less than the mean Vmax (620 nmol/min/mg) measured for the isomerase activity of the wild-type and native placental enzymes. In microsomal preparations, isomerase activity was completely abolished in the Y253,254F mutant enzyme, but Y253,254F had 45% of the 3beta-HSD activity of the wild-type enzyme. In contrast, the purified Y253F, wild-type and native enzymes had similar Vmax values for substrate oxidation by the 3beta-HSD activity. The 3beta-HSD activities of the Y253F, Y253,254F and wild-type enzymes reduced NAD+ with similar kinetic values. Although NADH activated the isomerase activities of the H261R and wild-type enzymes with similar kinetics, the activation of the isomerase activity of H261R by NAD+ was dramatically decreased. Based on these kinetic measurements, His261 appears to be a critical amino acid residue for the 3beta-HSD activity, and Tyr253 or Tyr254 participates in the isomerase activity of human type I (placental) enzyme.

Amino Acid Sequence↗
PubMed1998

Metoclopramide enhances labetalol-induced antihypertensive effect during handgrip in hypertensive patients.

The effects of metoclopramide, labetalol, and metoclopramide plus labetalol treatments on baseline cardiovascular parameters and isometric handgrip-induced changes were evaluated in 11 hypertensive subjects. Although all treatments were effective in reducing resting systolic (SBP) and diastolic (DBP) blood pressures, the combination of metoclopramide and labetalol appeared to provide a greater decrease (changes in SBP/DBP: 15/11 mm Hg, P < 0.05; from 149 +/- 4/95 +/- 4 mm Hg to 134 +/- 5/84 +/- 3 mm Hg) than did labetalol alone (changes in SBP/DBP: 10/9 mm Hg, P < 0.05; from 149 +/- 4/95 +/- 4 to 139 +/- 4/86 +/- 3 mm Hg). At 2 minutes, handgrip increased blood pressure on placebo (changes in SBP/DBP: 34/7 mm Hg, P < 0. 001). In the presence of metoclopramide and metoclopramide plus labetalol, however, handgrip induced lesser increases in blood pressure (changes in SBP/DBP: 23/7 mm Hg, P < 0.01, and 18/4 mm Hg, P < 0.01, for metoclopramide and metoclopramide plus labetalol treatments). We conclude that (1) metoclopramide lowers blood pressure in hypertensive patients; (2) metoclopramide attenuates blood pressure response to isometric handgrip; and (3) both compounds, labetalol and metoclopramide, seem to have a pharmacologic interaction concerning blood pressure decrease. A clinical significance is suggested for the metoclopramide effect.

Antihypertensive Agents↗
PubMed1998

Attenuated metoclopramide-induced vascular hyperreactivity to cold stress in athletic subjects.

We have previously reported a metoclopramide-induced vascular hyperreactivity to the cold pressor test (CPT) in normotensive and hypertensive subjects. The present study was designed to determine whether the state of physical training influences the cardiovascular responses to the CPT in normotensive subjects under metoclopramide (MTC) treatment. In 20 untrained subjects and 32 athletes (football players and runners), the blood pressure and heart rate responses to the CPT were studied after a 30-minute infusion of MTC (7.5 microg/kg per minute) and two placebo periods, before and after MTC, with 5% glucose solution. Under placebo conditions, the CPT produced significant increases of systolic blood pressure (SBP) in the untrained subjects and the runners, but not in the football players (17.2, 17.8, and 6.5 mm Hg for untrained subjects, runners, and football players, respectively). The runners responded with a lesser increase in diastolic blood pressure (DBP) during the CPT than did the others (15.8, 17.9, and 18.2 mm Hg for runners, untrained subjects, and football players, respectively). In the presence of MTC, the CPT induced a larger increase in blood pressure (SBP/DBP) in the untrained subjects (21.4/24.1 mm Hg) than in the football players (10/18.7 mm Hg) and runners (18.7/13.9 mm Hg). MTC diminished the hyperreactivity responses to the CPT in the trained subjects (41 and 56% for football players and runners, respectively). Our conclusions are as follows: (1) Vascular responses to cold stress are attenuated in athletic subjects compared with untrained subjects. (2) The metoclopramide-induced vascular hyperreactivity, formerly reported for normotensive and hypertensive subjects, seems to be absent in trained subjects. (3) It is suggested that a probable dopaminergic system adaptation occurs during exercise.

Adult↗
PubMed1998

Isozymes of the Na-K-ATPase: heterogeneity in structure, diversity in function.

The Na-K-ATPase is characterized by a complex molecular heterogeneity that results from the expression and differential association of multiple isoforms of both its alpha- and beta-subunits. At present, as many as four different alpha-polypeptides (alpha1, alpha2, alpha3, and alpha4) and three distinct beta-isoforms (beta1, beta2, and beta3) have been identified in mammalian cells. The stringent constraints on the structure of the Na pump isozymes during evolution and their tissue-specific and developmental pattern of expression suggests that the different Na-K-ATPases have evolved distinct properties to respond to cellular requirements. This review focuses on the functional properties, regulation, and possible physiological relevance of the Na pump isozymes. The coexistence of multiple alpha- and beta-isoforms in most cells has hindered the understanding of the roles of the individual polypeptides. The use of heterologous expression systems has helped circumvent this problem. The kinetic characteristics of different Na-K-ATPase isozymes to the activating cations (Na+ and K+), the substrate ATP, and the inhibitors Ca2+ and ouabain demonstrate that each isoform has distinct properties. In addition, intracellular messengers differentially regulate the activity of the individual Na-K-ATPase isozymes. Thus the regulation of specific Na pump isozymes gives cells the ability to precisely coordinate Na-K-ATPase activity to their physiological requirements.

Animals↗
PubMed1998

Absence of blood parasites in Griffon vultures from Spain.

Hematozoan parasites were not found on blood smears fron any of 82 Griffon vultures (Gyps fulvus) examined from Spain. These vultures represented samples of diverse temporal and spatial origin, and there was a great disparity in host ages (nestlings to > 5-yr-old adults) and physiological condition (growing, food-stressed, injured, and healthy birds).

Age Factors↗