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Biomedical subjects

N Fernández

Publications and source records attributed to N Fernández.

At least 19 recordsLinked to original sources
PubMed2003

Integrative assessment of marine pollution in Galician estuaries using sediment chemistry, mussel bioaccumulation, and embryo-larval toxicity bioassays.

An integrative assessment of environmental quality was carried out in selected sites along the Galician coast (NW Iberian Peninsula) combining analytical chemistry of seawater and sediments, bioaccumulation in the marine mussel, and embryo-larval sediment toxicity bioassays, in order to link biological and chemical criteria for the assessment of coastal pollution. Maximum values of Hg and Cu in seawater, sediment and mussels, were found in the inner part of Ria of Pontevedra, while maximum levels of organics (polychlorinated biphenyls, hexachlorobenzene and aldrin) were found in mussels from A Coruña. Outstanding values of Cu, Pb and Zn have been found in seawater and sediment from a single site, P3, which also was the most toxic in the embryo-larval bioassays performed with four different phyla of marine organisms: mollusks, echinoderms, arthropods and chordates. Sediment quality effects range-median values provided a valuable reference to predict biological effects from sediment chemistry data, while effects range-low values were too conservative. Sediment toxicity could also be predicted by using a toxic-unit model based on published EC50 values for trace metals and mobilization factors independently obtained from measurements of metal contents in sediments and their elutriates. When chemical and toxicological data are independently used to arrange sampling sites by using non-metric multidimensional scaling, a remarkable degree of concordance between both types of configurations could be observed.

Animals↗
PubMed2003

Assessment of coastal marine pollution in Galicia (NW Iberian Peninsula); metal concentrations in seawater, sediments and mussels (Mytilus galloprovincialis) versus embryo-larval bioassays using Paracentrotus lividus and Ciona intestinalis.

Sediments from three Galician Rias were tested for toxicity using sea-urchin and ascidian sediment elutriate embryo-larval bioassays. Trace metal contents in seawater, sediments and mussels were also determined and subjected to multidimensional scaling methods which grouped stations according to chemical contamination. High metal contents were found in seawater, sediments and mussels from the Ria of Pontevedra, and moderate levels were detected in the Ria of Vigo and Ria of Arousa. The results revealed that samples assessed as toxic, according to the sea-urchin and ascidian embryo-larval bioassays, were among the most polluted by trace metals. A good agreement was reported between ordination plots resulting from applying multidimensional scaling to the chemical data, and the results of the biological endpoints tested.

Animals↗
PubMed2003

Influence of pulsation rate on udder health and teat thickness changes in dairy ewes.

In this work on machine milking of ewes, pulsation rates of 120 and 180 cycles per min were compared, both with a pulsation ratio of 50:50 and a vacuum level of 36 kPa, comparing intramammary infection (IMI), somatic cell count (SCC) and teat end thickness changes. To this end, two groups of 20 Manchega ewes were used in a crossover experimental design with two experimental periods of 24 d for each. Bacterial exposure of all teats was increased by dipping them in a suspension of Staphylococcus simulans at four consecutive milkings of each period. Pulsation rate of 180 cycles per min, compared with 120 cycles per min, had no negative effect upon new IMI (11 and 16% of ewes infected, respectively) and SCC. No teat end lesions were observed in those animals milked with the two pulsations assayed. Also, teat thickness changes (-0.38 and -0.36 mm at 120 and 180 cycles per min, respectively) were not affected significantly. Finally, in absence of IMI, the two pulsation rates assayed did not affect the SCC.

Animals↗
PubMed2002

Therapeutic effects of psyllium in type 2 diabetic patients.

OBJECTIVE: The aim of this study was to evaluate the effects of psyllium in type 2 diabetic patients. DESIGN: The study included three phases: phase 1 (1 week), phase 2 (treatment, 14 g fibre/day, 6 weeks) and phase 3 (4 weeks). At the end of each phase a clinical evaluation was performed after the ingestion of a test breakfast of 1824.2 kJ (436 kcal). Measurements included concentrations of blood glucose, insulin, fructosamine, GHbA(1c), C-peptide and 24 h urinary glucose excretion. In addition, uric acid, cholesterol and several mineral and vitamin concentrations were also evaluated. SETTING: The study was performed at the Department of Pharmacology, Toxicology and Nursing at the University of León (Spain). SUBJECTS: Twenty type 2 diabetic patients (12 men and 8 women) participated in the study with a mean age of 67.4 y for men and 66 y for women. The mean body mass index of men was 28.2 kg/m(2) and that of women 25.9 kg/m(2). RESULTS: Glucose absorption decreased significantly in the presence of psyllium (12.2%); this reduction is not associated with an important change in insulin levels (5%). GHbA(1c), C-peptide and 24 h urinary glucose excretion decreased (3.8, 14.9 and 22.5%, respectively) during the treatment with fibre (no significant differences) as well as fructosamine (10.9%, significant differences). Psyllium also reduced total and LDL cholesterol (7.7 and 9.2%, respectively, significant differences), and uric acid (10%, significant difference). Minerals and vitamins did not show important changes, except sodium that increased significantly after psyllium administration. CONCLUSIONS: The results obtained indicate a beneficial therapeutic effect of psyllium (Plantaben) in the metabolic control of type 2 diabetics as well as in lowering the risk of coronary heart disease. We also conclude that consumption of this fibre does not adversely affect either mineral or vitamin A and E concentrations. Finally, for a greater effectiveness, psyllium treatment should be individually evaluated.

Aged↗
PubMed2002

The need for continuous immunosuppression with cyclosporin A to maintain an experimental model of uveal melanoma.

We investigated the need for continuous immunosuppression to maintain experimental tumours derived from human uveal melanoma cells implanted in the choroid of pigmented rabbits. Two groups of pigmented rabbits immunosuppressed with cyclosporin A (CsA) were implanted with human uveal melanoma cells in the suprachoroidal space. After 5 weeks, CsA was discontinued in group 2. Animals were treated with prophylactic antibiotics and examined weekly for tumour growth, weight and secondary effects; blood urea nitrogen levels were measured every two weeks. Autopsies and histopathological studies were performed after death or euthanasia at the end of week 12. The difference between the groups in the development of ophthalmoscopic tumours was not statistically significant 5 weeks after implantation. Tumours in group 1 grew progressively throughout the experiment, whereas group 2 tumours showed marked regression 3-4 weeks after discontinuing CsA. Tumours in group 1 were significantly larger and had greater mitotic activity and showed more ciliary body, optic nerve and extrascleral invasion than tumours in group 2, which showed massive fibrosis, minimal mitotic activity and marked inflammatory cell infiltration. Continuous immunosuppression with CsA seems to be necessary to maintain tumour growth in this experimental model of uveal melanoma.

Animals↗
PubMed2001

Diabetes abolishes the gender difference in vasopressin-mediated potentiation of sympathetic vasoconstriction.

Electrical field stimulation (4 Hz, 0.2 ms pulse duration, at a supramaximal voltage of 70 V, for 1 s) of isolated rat tail artery segments produced contraction which was lower in female than in male rats, and was reduced by streptozotocin-induced diabetes in both genders. This contraction was potentiated by vasopressin (10(-12)-10(-10) M) more in normoglycemic male than in normoglycemic female rats, and this effect of vasopressin was increased by the cyclooxigenase inhibitor meclofenamate (10(-5) M) in female control rats, but not in diabetic female, or control and diabetic male rats, and it was not modified by the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 10(-4) M). Endothelin-1 (10(-10)-3 x 10(-9) M) also potentiated the contraction to electrical stimulation. This potentiation was similar in all experimental groups, and it was not modified by meclofenamate or L-NAME. These results suggest that the potentiating effect of vasopressin, but not that of endothelin-1, on the sympathetic vasoconstriction, is lower in females than in males, probably by an increased release of vasodilating prostanoids, and this release may be reduced by diabetes in females.

Animals↗
PubMed2001

Adrenergic vasoconstrictor activity in the cerebral circulation after inhibition of nitric oxide synthesis in conscious goats.

The interaction between nitric oxide (NO) and adrenergic activity in the cerebral circulation was studied using conscious goats, where blood flow to one brain hemisphere (cerebral blood flow) was electromagnetically measured, and the effects of phentolamine and hexamethonium on cerebrovascular resistance were evaluated before (control) and after inhibition of NO synthesis with NW-nitro-L-arginine methyl ester (L-NAME). L-NAME (12 goats, 40 mg kg(-1) administered i.v.) reduced cerebral blood flow from 62 +/- 3 to 44 +/- 2 ml min(-1), increased mean systemic arterial pressure from 100 +/- 3 to 126 +/- 4 mm Hg, decreased heart rate from 79 +/- 5 to 50 +/- 4 beats min(-1) and increased cerebrovascular resistance from 1.63 +/- 0.08 to 2.91 +/- 0.016 mm Hg ml(-1)min(-1) (all P < 0.01). These hemodynamic variables normalized 48-72 h after L-NAME administration. Phentolamine (six goats, 1 mg), injected into the cerebral circulation. increased cerebral blood flow without changing systenic arterial pressure, but its cerebrovascular effects were augmented for about 24 h after L-NAME. The decrements in cerebrovascular resistance induced by phentolamine, in mm Hg ml(-1) min(-1), were: under control, 0.42 +/- 0.05; immediately after L-NAME, 1.38 +/- 0.09 (P < 0.01 compared with control); by about 24 h after L-NAME, 0.71 +/- 0.09 (P < 0.05 compared with control); and by about 48 h after L-NAME, 0.40 +/- 0.07 (P > 0.05 compared with control). Hexamethonium (six goats, 0.5-1 mg kg(-1) min(-1) i.v.) decreased mean systemic arterial pressure to about 75 mm Hg and caused tachycardia similarly before and after L-NAME, but the decrements in cerebrovascular resistance were augmented for about 24 h after L-NAME. The decrements in cerebrovascular resistance induced by hexamethonium, in mm Hg ml(-1).min(-1), were: under control. 0.61 +/- 0.09, immediately after L-NAME, 1.33 +/- 0.16 (P < 0.01 compared with control); by about 24 h after L-NAME, 1.18 +/- 0.10 (P < 0.01 compared with control): and by about 48 h after L-NAME, 0.99 +/- 0.10 (P > 0.05 compared with control). Therefore, these results suggest that adrenergic vasoconstrictor tone in cerebral vasculature may be augmented after inhibition of NO synthesis, and that this increment may contribute to the reduction of cerebral blood flow after inhibition of NO formation.

Adrenergic alpha-Antagonists↗
PubMed2001

FcgammaRIIA exogenously expressed in HeLa cells activates the mitogen-activated protein kinase cascade by a mechanism dependent on the endogenous expression of the protein tyrosine kinase Syk.

HeLa cells transfected to express the human Fc receptor FcgammaRIIA were stimulated with aggregates of IgG, IgG-ovalbumin equivalence immune complexes and monoclonal antibody reacting with FcgammaRIIA. All of these stimuli activated the cells as judged from the band-shift characteristic of the activation of the p42-MAP/ERK kinase. Since this response is currently associated with the activation of the protein tyrosine kinase Syk, the expression of which is currently thought to be restricted to hemopoietic cells, the results were considered as an indirect evidence of the expression in HeLa cells of either Syk or another protein tyrosine kinase accounting for the same function. Transfection with a dominant negative Syk mutant abrogated the response to FcgammaRIIA cross-linking, whereas overexpression of Syk did not increase the extent of the response. Further evidence of the expression of syk was obtained by the reverse transcription PCR approach and sequencing of the DNA bands. Moreover, immunoprecipitation with anti-Syk antibody of the cell lysates obtained after cross-linking of FcgammaRIIA followed by immunoblotting with anti-phosphotyrosine antibody showed the phosphorylation of a protein band migrating as Syk. These data indicate that expression of FcgammaRIIA on epithelial HeLa cells conveys signals to the p42-MAP/ERK kinase by a mechanism involving the recruitment of Syk. In contrast, cross-linking of this receptor does not yield productive signals coupled to other responses associated to the FcgammaR system such as triggering of the arachidonic acid cascade, activation of the NF-kappaB system and production of chemotactic cytokines.

Animals↗
PubMed2001

Combined toxicity of dissolved mercury with copper, lead and cadmium on embryogenesis and early larval growth of the Paracentrotus lividus sea-urchin.

The individual and combined toxicity of dissolved mercury, copper, lead and cadmium has been investigated by using the Parcentrotus lividus sea-urchin embryo-larval bioassay. Embryogenesis success and early larval growth have been recorded after incubation of fertilised eggs in seawater, both with single metals and binary combinations of Hg with every other metal. For individual metals the ranking of toxicity was Hg > Cu > Pb > Cd, with EC50 values of 21.9, 66.8, 509 and 9240 micrograms/l, respectively. Lowest observed effect concentrations (LOEC) for early larval growth were approximately three times lower than the EC50 values for Hg, Cu and Pb, and more than two orders of magnitude lower for Cd, emphasizing the danger of underestimating toxicity when only lethal effects are recorded. Marking & Dawson's additive indices ranged from 0.10 to 0.19, indicating additive effects with a slight trend to synergism, which was statistically significant for the Hg-Pb combination only. Hayes' additive indices were within the margins considered acceptable to describe additive interactions.

Animals↗
PubMed2001

Cerebral vasoconstriction produced by vasopressin in conscious goats: role of vasopressin V(1) and V(2) receptors and nitric oxide.

To examine the role of vasopressin V(1) and V(2) receptors, nitric oxide and prostanoids in the cerebrovascular effects of arginine vasopressin, cerebral blood flow was electromagnetically measured in awake goats. In 16 animals, vasopressin (0.03 - 1 microg), injected into the cerebral circulation, caused increments of resting cerebrovascular resistance which ranged from 18% (0.03 microg, P<0.01) to 79% (1 microg, P<0.01). Desmopressin (0.03 - 1 microg, four goats) did not affect significantly cerebrovascular resistance. The cerebrovascular resistance increases by vasopressin were reduced significantly by the antagonist for vasopressin V(1) receptors d(CH(2))(5)Tyr(Me)-AVP in a rate depending way (five (six goats) and 15 (four goats) microg min(-1)), and by the mixed antagonist for vasopressin V(1) and V(2) receptors desGly-d(CH(2))(5)-D-Tyr(Et)Val-AVP (5 microg min(-1), four goats), and they were not significantly affected by the antagonist for vasopressin V(2) receptors d(CH(2))(5), D-Ile(2), Ile(4)-AVP (5 microg min(-1), four goats). The inhibitor of nitric oxide synthesis N(w)-nitro-L-arginine methyl ester (L-NAME, 47 mg kg(-1) i.v., five goats) augmented cerebrovascular resistance by 130% (P<0.01), and for 24 h after this treatment the cerebrovascular effects of vasopressin were potentiated. The inhibitor of cyclo-oxygenase meclofenamate (6 mg kg(-1) i.v., five goats) did not modify significantly resting haemodynamic variables measured or the cerebrovascular effects of vasopressin. Therefore, the vasopressin-induced cerebral vasoconstriction may be mediated by vasopressin V(1) receptors, without involvement of vasopressin V(2) receptors, and may be modulated by nitric oxide but not by prostanoids.

Animals↗
PubMed2001

Effects of ispaghula husk and guar gum on postprandial glucose and insulin concentrations in healthy subjects.

OBJECTIVE: The aim of this study was to evaluate, under the same experimental conditions and in the same subjects, the effects of ispaghula husk and guar gum on postprandial glucose and insulin concentrations in healthy female subjects. DESIGN: An oral glucose load with and without fiber was administered in the morning after an overnight fast. The study of the fiber effect was planned according to a randomized and cross-over design. SETTING: The study was performed at the Department of Pharmacology, Toxicology and Nursing at the University of León (Spain). SUBJECTS: Ten healthy female volunteers aged 30-48 y with normal body mass indices participated in this study. RESULTS: A significant decrease in mean serum insulin concentrations was observed from 30 to 90 min in the presence of both fibers. The area under the insulin curve was significantly reduced by 36.1% for ispaghula husk and 39.4% for guar gum. The area under the glucose curve was reduced by 11.1% (significant difference) for ispaghula husk and 2.6% for guar gum (no significant difference). CONCLUSIONS: According to the results obtained in this study, the administration of ispaghula husk may be beneficial due to its ability to reduce glucose postprandial concentration and especially insulin requirements. Individualization of the treatment would be advisable due to large individual variations observed in glycemic and insulinemic postprandial responses.

Adult↗
PubMed2001

Influence of parenteral nutrition on postoperative recovery in an experimental model of peritonitis.

BACKGROUND AND AIMS: There seems to be no clear-cut indications for routine TPN support after major elective surgery. The present study was designed to investigate whether TPN could improve the results of standard surgical care for acute peritonitis (laparotomy plus antibiotics). ANIMALS AND METHODS: Peritonitis was induced in 48 New Zealand rabbits (day -2). On day 0, appendectomy and peritoneal lavage were performed, ceftriaxone (250 mg, i.m./24 h.) was started and animals were randomly assigned to receive regular fluids (RF), glucose-based TPN (G-TPN) or isocaloric fat-based TPN (F-TPN) for 6 days. MAIN OUTCOME MEASURES: Balance studies (days 1-3), s-albumin, thyroid hormones and urinary catecholamines were determined at various points of the experiment. At postmortem, wound infection, residual intra-abdominal infection and laparotomy wound breaking strength were recorded. RESULTS: Peritonitis produced a fall in weight, s-albumin and T3. At day 6, weight-loss was more pronounced in RF than in G-TPN or F-TPN (-7 vs 1.5 vs -1.2%;P=0.0001) but s-albumin and T3 concentrations were similar. Diuresis (377 vs 268 vs 269 mL/3 days; P=0.01) was higher and water balance lower (373 vs 511 vs 480 mL/3 days; P=0.01) in Group RF. Although the differences were not statistically significant (P<0.2), persistent infection and wound breaking strength were slightly worse in the pooled TPN groups compared with the RF group (19 vs 6% and 542 vs 701 g, respectively). CONCLUSIONS: TPN failed to improve relevant biochemical markers and clinical outcome after laparotomy for peritonitis.

Acute Disease↗
PubMed2001

Analysis time and lactation stage influence on lactoperoxidase system components in dairy ewe milk.

To study the effect of time elapsed from the moment of taking samples on lactoperoxidase system components, we analyzed the activity of the lactoperoxidase enzyme and the concentrations of thiocyanate and hydrogen peroxide in 46 individual samples of Manchega ewe milk. Samples were maintained at a temperature of 4 degrees C until analysis, which took place at 6, 12, 24, and 48 h after extraction. Decreases were observed in lactoperoxidase activity when the analyses were performed at 48 h and in the thiocyanate and hydrogen peroxide concentrations at 12 h compared with those carried out earlier. Consequently, when the components of the lactoperoxidase system or its antibacterial activity are studied, the time elapsed since the sampling commenced must be taken into account. Similarly, the time elapsed is important when carrying out bacterial counts or residue screening by microbiological methods, during which the lactoperoxidase system may interfere. To study the component changes in the lactoperoxidase system during lactation, samples obtained 15, 30, 45, 60, 75, 90, 105, 120, and 135 d postpartum from 48 Manchega ewes were used. Average lactoperoxidase activity, thiocyanate, and hydrogen peroxide concentrations were 3.46 U/ml, 6.89 mg/L, and 0.39 mg/L, respectively, with significant variations throughout lactation. The thiocyanate and hydrogen peroxide levels at different lactation stages seemed to be insufficient to activate the lactoperoxidase system. Nevertheless, this could be achieved by adding 5 mg/L of thiocyanate and 8 mg/L of hydrogen peroxide at any time during lactation.

Animals↗
PubMed2001

Use of activated carbon and natural zeolite as support materials, in an anaerobic fluidised bed reactor, for vinasse treatment.

In Cuba, the alcohol distillation process from cane sugar molasses, produces a final waste (vinasse), with an enormous polluting potential and a high sulfate content. Applying the anaerobic technology, most of the biodegradable organic matter can turn into biogas, rich in methane but with concentrations of sulfide above 1%. The present work develops two experiences with anaerobic fluidized bed reactors (AFBR) using both Cuban raw material, activated carbon and natural zeolite, as support media, with the purpose of obtaining high organic matter removal rates and keeping sulfide and ammonium concentrations in the permissible ranges. The reactors were operated during 120 days, achieving an organic loading rate of 10 kg COD/m3 day, with COD removal above 70%, and a methane production of 2 L/d. The activated carbon and natural zeolite used support materials in anaerobic fluidized bed reactors, and showed good results of distillery waste removal.

Alcoholic Beverages↗
PubMed2001

[Efficacy of direct paraffin embedding in cytological analysis of vitreous from proliferative vitreo-retinopathy (PVR)].

PURPOSE: To assess the efficacy of direct paraffin embedding in cytological analysis of vitreous samples in patients suffering from PVR, against the commonly used method for this purpose (cytospin). METHOD: Undiluted vitreous or vitreous fluids from 40 subsequent patients with PVR were collected and processed (samples collected from cassette at the end of aspiration line in final stage of vitrectomy process). 40 samples underwent cytospinning, 24 samples were paraffin embedded. Specimens were assessed by an expert ocular pathologist and tested samples were assigned to scoring and non scoring groups (where scoring means at least three cells per field in x60 magnification). RESULTS: All 24 paraffin embedding samples scored according to criteria while 36 of 40 cytospinned samples complied with scoring criteria. Differences were not statistically significant. Macrophages (87.5%) and pigmented cells (85%) were the most frequent findings. CONCLUSIONS: Direct paraffin embedding is useful for cytological studies in vitreous samples of PVR patients.

Humans↗
PubMed2001

Combining the biological nitrogen and sulfur cycles in anaerobic conditions.

The biochemical processes involved in the anaerobic degradation of carbon, nitrogen and sulfur compounds can be represented by an oxidation-reduction or electron donor-acceptor scheme. The theoretic values of Gibbs free energy (deltaG0) calculated from thermodynamic data indicate the feasibility of the reactions. The interactions C-S and C-N are well known but there is a lack of information about the interaction N-S. The anaerobic transformation of nitrates using reduced sulfur compounds can be explained considering that nitrate acts as electron acceptor while reduced sulfur compounds are the electron donors. A new N-S interaction in anaerobic conditions (ORP = -425 mV) has been experimentally observed when treating industrial wastewater rich in organic nitrogen and sulfate. The mass balances of the different nitrogenous and sulfur compounds in the liquid and gas phases clearly indicated an uncommon evolution. An important percentage of the nitrogen entering the reactor as TKN was removed from the liquid phase appearing as N2 in the gas phase. Simultaneously, only part of the sulfate initially present in the influent appeared as sulfide in the effluent or as hydrogen sulfide in the gas. These experimental observations may suggest a new anaerobic N-S biological interaction involving simultaneous anaerobic ammonium oxidation and sulfate reduction, ammonium being the electron donor and sulfate the electron acceptor.

Bacteria, Anaerobic↗