Biomedical subjects

F Ibarra

Publications and source records attributed to F Ibarra.

At least 19 recordsLinked to original sources

PubMed2006

Immature triclabendazole-resistant Fasciola hepatica: tegumental responses to in vitro treatment with the sulphoxide metabolite of the experimental fasciolicide compound alpha.

Juvenile triclabendazole-resistant liver flukes, Fasciola hepatica, were incubated in vitro with 10 microg/ml of the sulphoxide metabolite of the experimental fasciolicide, compound alpha [5-chloro-2-methylthio-6-(1-naphthyloxy)-1H-benzimidazole], for 6 and 18 h. Following treatment, the specimens were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tubulin immunocytochemistry. The SEM results revealed a posterior-directed disruption comprised predominantly of swelling and blebbing of the tegument; these changes were more severe and extensive after the longer 18-h incubation. Along with swelling of the tegument and blebbing, the TEM results also revealed swelling of the mitochondria and basal infolds. A decrease in the number of both T1 and T2 secretory bodies was observed in the syncytium and cytoplasmic connections after the 18-h treatment. The circular muscle bundles were also disrupted, in that the organisation of the muscle fibres was irregular and the total number of muscle fibres was reduced. The immunocytochemical studies revealed no significant disruption to the distribution of tubulin immunoreactivity within the tegumental syncytium, the cytoplasmic connections or the associated tegumental cells. The results indicate that alpha.SO is capable of disrupting the tegument of 4-week-old triclabendazole-resistant liver flukes, though the morphological changes were not associated with any significant differences in tubulin immunostaining.

Animals↗

PubMed2006

Adult triclabendazole-resistant Fasciola hepatica: surface and subsurface tegumental responses to in vitro treatment with the sulphoxide metabolite of the experimental fasciolicide compound alpha.

Mature Fasciola hepatica of the triclabendazole-resistant Sligo isolate were incubated in vitro with 10 microg/ml of the sulphoxide metabolite of compound alpha [5-chloro-2-methylthio-6-(1-naphthyloxy)-H-benzimidazole]; the metabolite will be referred to as alpha.SO. Changes resulting from drug treatment were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tubulin immunocytochemistry (ICC). SEM revealed that disruption to the tegumental surface mainly took the form of swelling and blebbing. Extensive spine loss occurred on the ventral surface of the oral cone, and sloughing of the tegument was observed along the lateral margins of the fluke. Examination of sections from the anterior mid-body region at the TEM level revealed that treatment with alpha.SO led to swelling of the basal infolds and mitochondria within the tegumental syncytium; also, accumulations of secretory bodies beneath the apical plasma membrane. The tegumental cell bodies contained swollen mitochondria and cisternae of granular endoplasmic reticulum, but few Golgi complexes were observed. An increase in T2 secretory bodies was observed, whilst in the T1 tegumental cells, the T1 secretory bodies had decreased in number. Immunocytochemical (ICC) studies showed that incubation with alpha.SO, ABZ.SO and TCBZ.SO did not cause significant changes to the distribution of tubulin within the tegumental syncytium of the Sligo isolate. In contrast, alpha.SO, ABZ.SO and TCBZ.SO caused severe disruption to tubulin organization within the syncytial layer of the TCBZ-susceptible Cullompton isolate. The EM results confirm that compound alpha is a fasciolicide capable of disrupting the tegument of mature TCBZ-resistant F. hepatica; however, this was not accompanied by any change in tubulin immunoreactivity.

Animals↗

PubMed2006

Determination of the maximum tolerated dose and the safety index of an experimental fasciolicide in cattle.

The aim of the present study was to determine the maximum tolerated dose (MTD) and the safety index (SI) of 5-chloro-2-methylthio-6-(1-napthyloxy)1H-benzimidazole, called compound alpha, in cattle. In addition, to search for possible adverse effects after treatment, the measurement of some biochemical, haematological and physiological parameters were also analysed. Eighteen crossbred heifers were divided into six groups of three animals each. Groups 1-5 received a single oral dose of 12, 36, 60, 120 and 180 mg/kg of body weight (bw) of compound alpha. Group 6 served as an untreated control. To determine the biochemical, haematological and enzymatic parameters, sera and blood samples were individually taken at 0, 4, 8, 16, 32, 128, and 720 h after treatment. Physiological parameters such as rectal temperature, heart rate (HR), respiration rate (RR) and ruminal motility were measured at the time intervals mentioned above. Estimation of the MTD and SI was obtained by using the formula reported by the Food and Drug Administration (FDA), the results showing an MTD of 180 mg/kg/bw and an SI of 15 times the recommended clinical dose. Some statistical differences were observed in a few of the biochemical, haematological and enzymatic parameters, the adverse effects being not highly representative. Alterations on HR and RR were statistically different (P<0.05) only in heifers treated with 180 mg.

Administration, Oral↗

PubMed2003

Do social parasitic bumblebees use chemical weapons? (Hymenoptera, Apidae).

The bumblebee Bombus (Psithyrus) norvegicus Sp.-Schn. is an obligate social parasite of B. (Pyrobombus) hypnorum L. Behavioural observations indicated that nest-invading B. norvegicus females may use allomones to defend themselves against attacking host workers. However, so far no defensive chemicals used by social parasitic bumblebee females have been identified. We analysed volatile constituents of the cuticular lipid profile of B. norvegicus females. Furthermore, we performed electrophysiological studies and behavioural experiments in order to identify possible chemical weapons. Coupled gas chromatography-electroantennography showed 15 compounds to trigger responses in antennae of the host workers. Using gas chromatography-mass spectrometry, the main compound among the cuticular volatiles of B. norvegicus females was found to be dodecyl acetate. A corresponding mixture of synthetic volatiles as well as pure dodecyl acetate showed a strong repellent effect on starved host workers. B. norvegicus females use dodecyl acetate to repel attacking B. hypnorum workers during nest usurpation and subsequently during colony development. Dodecyl acetate is the first repellent allomone identified in bumblebees.

Acetates↗

PubMed2001

Effect of parasite burden on the detection of Fasciola hepatica antigens in sera and feces of experimentally infected sheep.

The effect of Fasciola hepatica parasite burden on the detection of excretory/secretory (E/S) antigens in sera and feces of experimentally infected sheep was evaluated using a double antibody-based capture enzyme-linked immunosorbent assay (ELISA). Four groups of five sheep each were used. The first three groups were infected with 50, 100 and 200 metacercariae of F. hepatica, and the fourth group remained as non-infected control. On the day of infection and weekly thereafter, serum and fecal samples were taken. ELISA detected F. hepatica E/S antigen levels in serum from the first week post-infection (wpi) and in fecal supernatant from the fourth wpi, which were significantly (p<0.05) higher than controls. F. hepatica eggs were not detected until after the eighth wpi. The correlation between absorbance of E/S antigens in serum with the fluke burden was 0.77 (p<0.0001) and in feces 0.76 (p<0.0001) at 12th wpi. The sensitivity of the assay to detect E/S antigens in serum was 86.6% and in feces 93.3%. It is concluded that the ELISA technique used in this study offers a diagnostic alternative for detecting early infections of F. hepatica in sheep.

Animals↗

PubMed2001

Neosporosis in Mexican dairy herds: lesions and immunohistochemical detection of Neospora caninum in fetuses.

Of 211 aborted bovine fetuses collected from Mexican dairy herds between January 1996 and March 1999, 73 showed microscopical lesions consistent with neosporosis. Of these 73 fetuses, 58 (79%) showed lymphocytic myocarditis, 39 (53%) showed microgliosis and multifocal necrosis in the brain, 39 (53%) showed lymphocytic hepatitis, and 19 (26%) showed lymphocytic myositis. Immunohistochemical examination of brain, myocardium and liver from 53 of the same 73 fetuses demonstrated Neospora caninum antigens in 41 (77%), of which 19 (46%) gave positive results in one of the three sites, 15 (37%) in two, and seven (17%) in three. The results indicated the presence of neosporosis in a number of the main dairy farming regions of Mexico.

Abortion, Veterinary↗

PubMed2001

Seroprevalence study of bovine neosporosis in Mexico.

An indirect enzyme-linked immunosorbent assay was used to obtain epidemiologic information on bovine neosporosis in dairy herds of the Mexican central plateau. Sera were collected from 1,003 cows from 50 dairy herds. Forty-three herds (group A) had been experiencing a high abortion rate. The abortion rates for the remaining 7 herds (group B) were within normal limits for Mexico. Five-hundred sixty-one (56%) of the 1,003 sera were positive. The seroprevalence of Neospora caninum antibodies was 72% (95% CI = 68-75%) in group A and 36% (95% CI = 31-40%) in group B. These results clearly show that infection with N. caninum is widespread in Mexican dairy herds, as indicated by seropositive cows in group A and group B herds at the time of the sample collection.

Animal Husbandry↗

PubMed2000

Sex pheromone mimicry in the early spider orchid (ophrys sphegodes): patterns of hydrocarbons as the key mechanism for pollination by sexual deception.

We investigated the female-produced sex pheromone of the solitary bee Andrena nigroaenea and compared it with floral scent of the sexually deceptive orchid Ophrys sphegodes which is pollinated by Andrena nigroaenea males. We identified physiologically and behaviorally active compounds by gas chromatography with electroantennographic detection, gas chromatography-mass spectrometry, and behavioral tests in the field. Dummies scented with cuticle extracts of virgin females or of O. sphegodes labellum extracts elicited significantly more male reactions than odorless dummies. Therefore, copulation behavior eliciting semiochemicals are located on the surface of the females' cuticle and the surface of the flowers. Within bee and orchid samples, n-alkanes and n-alkenes, aldehydes, esters, all-trans-farnesol and all-trans-farnesyl hexanoate triggered electroantennographic responses in male antennae. Most of the alkanes and alkenes occurred in similar patterns both in the bees and orchids. O. sphegodes leaf extracts contained mostly the same compounds but in different proportions. In behavioral tests with synthetic compounds, blends of alkenes triggered significantly more approaches and pounces of the males whereas alkanes were not more attractive than odorless dummies. Since alkanes and alkenes together were most attractive, we conclude they constitute the bees' sex pheromone as well as the pseudocopulation-behavior releasing orchid-odor bouquet.

Adaptation, Biological↗

PubMed2000

Evolution of reproductive strategies in the sexually deceptive orchid Ophrys sphegodes: how does flower-specific variation of odor signals influence reproductive success?

The orchid Ophrys sphegodes Miller is pollinated by sexually excited males of the solitary bee Andrena nigroaenea, which are lured to the flowers by visual cues and volatile semiochemicals. In O. sphegodes, visits by pollinators are rare. Because of this low frequency of pollination, one would expect the evolution of strategies that increase the chance that males will visit more than one flower on the same plant; this would increase the number of pollination events on a plant and therefore the number of seeds produced. Using gas chromatography-mass spectrometry (GC-MS) analyses, we identified more than 100 compounds in the odor bouquets of labellum extracts from O. sphegodes; 24 compounds were found to be biologically active in male olfactory receptors based on gas chromatography with electroantennographic detection (GC-EAD). Gas chromatography (GC) analyses of odors from individual flowers showed less intraspecific variation in the odor bouquets of the biologically active compounds as compared to nonactive compounds. This can be explained by a higher selective pressure on the pollinator-attracting communication signal. Furthermore, we found a characteristic variation in the GC-EAD active esters and aldehydes among flowers of different stem positions within an inflorescence and in the n-alkanes and n-alkenes among plants from different populations. In our behavioral field tests, we showed that male bees learn the odor bouquets of individual flowers during mating attempts and recognize them in later encounters. Bees thereby avoid trying to mate with flowers they have visited previously, but do not avoid other flowers either of a different or the same plant. By varying the relative proportions of saturated esters and aldehydes between flowers of different stem positions, we demonstrated that a plant may take advantage of the learning abilities of the pollinators and influence flower visitation behavior. Sixty-seven percent of the males that visited one flower in an inflorescence returned to visit a second flower of the same inflorescence. However, geitonogamy is prevented and the likelihood of cross-fertilization is enhanced by the time required for the pollinium deposited on the pollinator to complete its bending movement, which is necessary for pollination to occur. Cross-fertilization is furthermore enhanced by the high degree of odor variation between plants. This variation minimizes learned avoidance of the flowers and increases the likelihood that a given pollinator would visit several to many different plants within a population.

Animals↗

PubMed1998

Comparison of three ELISA tests for seroepidemiology of bovine fascioliosis.

The aim of the present study was to compare the sensitivity, specificity and usefulness of the DIG-ELISA, DOT-ELISA and Indirect ELISA tests for determining the seroprevalence of fasciolosis in cattle under tropical conditions in Mexico. To standardize the tests, positive and negative sera to F. hepatica from 88 Holstein Freisian adult cows located in an enzootic area of fascioliosis and 88 crossbred adult cattle from a fluke-free area were used. For the epidemiological study, 85 crossbred cattle between 1 to 7 years of age were used. Animals were bled every two months, from March 1995 to September 1996 and the sera obtained were stored at -70 degrees C, until used. Indirect ELISA showed a sensitivity of 96.5% and a specificity of 98.8%, DIG-ELISA 97.5% and 80.0% and DOT-ELISA 93.1% and 95.4%, respectively. During 1995, Indirect ELISA yielded the highest levels of IgG anti-F. hepatica antibodies. However, in 1996, after animal treatment with triclabendazole, DIG-ELISA tended to show higher percentages of antibody-positive animals, but it was not significantly different (p>0.05) from the other tests. Comparisons made in parallel to the faecal sedimentation test demonstrated that all serological tests detected higher percentages of positive animals. Only one serum out of ten (10%) of Paramphistomum spp. cross-reacted with the DOT-ELISA test, but no cross-reaction was observed with sera from animals with other parasites. All ELISA tests were highly sensitive and specific; they may be recommended for use in seroepidemiological surveys for F. hepatica.

Animals↗

PubMed1993

Bidirectional regulation of Na+,K(+)-ATPase activity by dopamine and an alpha-adrenergic agonist.

Catecholamines have pronounced effects on the renal handling of sodium and water, dopamine-promoting sodium and water excretion, and norepinephrine-promoting sodium and water retention. In the present study, using isolated permeabilized renal tubule cells and intact rats, we have shown that these effects can be attributed to opposing actions of these transmitters on renal tubular Na+,K(+)-ATPase activity. The ability of each of these catecholamines to regulate Na+,K(+)-ATPase activity is affected by the concentration of Na+ as well as by the absence or presence of the opposing catecholamine.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1992

Calcineurin mediates alpha-adrenergic stimulation of Na+,K(+)-ATPase activity in renal tubule cells.

The alpha-adrenergic agonist oxymetazoline increased Na+,K(+)-ATPase activity of single proximal convoluted tubules dissected from rat kidney. Activation of the enzyme by oxymetazoline was prevented by either the alpha 1-adrenergic antagonist prazosin or the alpha 2-adrenergic antagonist yohimbine and was mimicked by the calcium ionophore A23187. The effect of oxymetazoline on Na+,K(+)-ATPase activity was prevented by a specific peptide inhibitor of calcineurin, as well as by FK 506, an immunosuppressant agent known to inhibit calcineurin; these results indicate that the action of oxymetazoline is mediated via activation of calcineurin (a calcium/calmodulin-dependent protein phosphatase). Activation of the Na+,K(+)-ATPase by either oxymetazoline or A23187 was associated with a greater than 2-fold increase in its affinity for Na+. The results provide a biochemical mechanism by which norepinephrine, released from renal nerve terminals, stimulates Na+ retention.

Animals↗

PubMed1992

[Two-dimensional and Doppler echocardiography in the non-invasive diagnosis of coronary cardiac fistula].

Two asymptomatic children with an atypical continuous murmur and a clinical diagnosis of coronary artery fistula are reported. Cross-sectional and Doppler echocardiography led to the diagnosis of a right coronary artery-right ventricule fistula in both cases, which was confirmed by coronary angiography. Surgical closure of the fistula was realized without complications.

Arteriovenous Fistula↗

PubMed1989

Voltage dependence and barium sensitivity of colonic K secretion in renal failure.

Net colonic K secretion (JKnet) is increased in rats and humans with chronic renal failure (CRF). To study whether transepithelial potential difference (PD), active transport forces and/or luminal K conductance play a role in this adaptation, experiments were performed in the colon of control, K-adapted, and CRF rats. Under basal conditions the PD in vivo in CRF was greater than in controls and not different from K-adapted rats. JKnet was comparable in vivo in CRF and K-adapted rats and was greater than in controls. Amiloride (10 microM) reduced PD and JKnet in K-adapted and CRF rats to levels comparable to controls. Under in vitro short-circuited conditions serosal-to-mucosal K flux (JKs----m) in distal colon was significantly increased in K-adapted and CRF animals compared with control, whereas barium caused a significant reduction in JKs----m in all groups of animals. The barium-sensitive component of K secretion was greater, however, in the two experimental groups (-0.2 +/- 0.02 and -0.2 +/- 0.07 in K-adapted and CRF animals, respectively, vs. -0.08 +/- 0.02 microeq.h-1.cm-2 in controls, P less than 0.05). However, luminal barium failed to completely inhibit the increase in K secretion observed in the experimental groups. These data suggest that an increase in PD that results in a rise in luminal negativity, stimulation of active transport, and an increase in barium-sensitive K channels and barium-insensitive pathways in apical membrane of distal colon participate in the mechanism by which net K secretion is increased in the large intestine of subjects with CRF.

Amiloride↗

PubMed1989

[Pericardial mesothelioma: apropos of a case].

We report a case of primary pericardial malignant mesothelioma in a 53-year old male with no asbestos previous exposure. The first clinical sign was a massive pericardial effusion causing hemodynamic disturbances. CT confirmed the initial ecochardiographic diagnosis. The patient underwent pericardiocentesis which improved his hemodynamic status as well as showed malignant cellularity in the liquid examination. Surgical treatment, including pericardiectomy and tumor resection, together with chemotherapy restored normal hemodynamics, the patient being now asymptomatic. We want to emphasize the rarity of this tumor and its insidious clinical presentation even leading to hemodynamic impairment, as well as the great value of echocardiography and CT in its diagnosis, although, in some cases, thoracotomy has been the only valid diagnostic procedure.

Heart Neoplasms↗

PubMed1988

Intravascular volume in cirrhosis. Reassessment using improved methodology.

Previous studies of blood volume (BV) in cirrhosis have either not adjusted BV properly for body size; determined plasma volume from the dilution of labeled albumin 10-20 min postinjection, when some extravascular redistribution has already occurred; and/or not used the correct whole body-peripheral hematocrit ratio (0.82) in calculating whole BV from plasma volume and the peripheral hematocrit. We measured BV with attention to these considerations in 19 patients with cirrhosis and reexamined the determinants of vascular volume and the relationship between vascular volume and sodium retention. BV was calculated as plasma volume (determined from extrapolated plasma activity of intravenously injected [131I]+albumin at time 0) divided by (peripheral hematocrit X 0.82). The result was expressed per kilogram "dry" body weight, determined by subtracting the mass of ascites (measured by isotope dilution; 1 liter = 1 kg) from the actual body weight of nonedematous patients. Measured and expressed in this way, BV correlated strongly with esophageal variceal size (r = 0.87, P less than 0.05), although not with net portal, right atrial, inferior vena caval, or arterial pressure, and was significantly greater in patients with sodium retention as compared to patients without sodium retention. The principal modifier of vascular volume in cirrhosis is vascular capacity, which is probably mainly determined by the extent of the portasystemic collateral circulation. Increased vascular volume in patients with sodium retention as compared to patients without sodium retention supports the "overflow" theory of ascites formation.

Adult↗

PubMed1987

Observations on the mechanism and location of ascites reabsorption in man.

Animal data indicate that ascites is reabsorbed by a lymphatic mechanism and that these vessels are subdiaphragmatic in location. We evaluated the relative role of lymphatics in ascites reabsorption in man by comparing the ascites clearance and plasma appearance rates of intraperitoneally injected radiolabeled albumin to those of intraperitoneally injected labeled autologous red blood cells, which require, owing to their large size, lymphatic removal, in patients with cirrhosis and ascites. To evaluate the location of reabsorption, we repeated these measurements after replacing ascites in the subdiaphragmatic region with 500-1000 ml of intraperitoneally injected air, reasoning that this maneuver should slow or eliminate ascites reabsorption occurring at this site. We found that the transfer rates of albumin and red cells out of ascites were similar and that creation of pneumoperitoneum did not influence these rates. These data confirm that ascites protein reabsorption occurs via a lymphatic mechanism in man. They suggest, however, that these vessels may not be subdiaphragmatic in location.

Absorption↗

PubMed1986

Rectification of the remnants of the leaflets--a new surgical technique to avoid periprosthetic leaks in aortic valve replacement.

During the last 12 years, we have used a modified suture technique for aortic valve replacement in 450 patients in order to avoid periprosthetic leaks. There were 420 survivors, and reoperation for periprosthetic leaks was necessary in no instance. The "secret" of our technique consists of the uniform distribution of the tensile forces among all sutures, eliminating uneven stresses that favors tearing of the tissues or rupture of the stitches.

Adolescent↗