Biomedical subjects

J Méndez

Publications and source records attributed to J Méndez.

At least 19 recordsLinked to original sources

PubMed2006

Toxoplasma gondii: cross-immunity against the enteric cycle.

Eight of nine cats inoculated with strain ME-49 and challenged with three different strains of Toxoplasma were immune to oocyst shedding, as ascertained with bioassays of their feces. In a second experiment, only toxoplasma asexual stages were seen in H&E stained gut sections of cats treated with suppressive doses of sulfamerazine and pyrimethamine starting 2 days after oral inoculation with cysts of the strain ME-49 and killed 6 days later. In a third experiment, four cats were similarly inoculated and treated for 20 days. Six weeks later, the cats received an oral homologous challenge with cysts, and none shed toxoplasma oocysts. An acceptable level of cross-protection was achieved with strain ME-49, and therefore, it can be used as a candidate strain from which antigens could be tested for enteric protection.

Animals↗

PubMed2006

Refinement of the mouse model of congenital toxoplasmosis.

The goals of the present investigation, focusing on the BALB/c mouse model of congenital toxoplasmosis, were: (1) to find a method to determine pregnancy in the mouse. The method has 100% sensitivity and 72% specificity; (2) to test congenital transmission during the chronic stage of toxoplasmosis. This occurred in 2 of 10 mice tested; (3) to investigate the relationship between the infective dose and the rate of congenital transmission. This was not demonstrated for doses of 10(2) to 10(3) bradyzoites and oocysts of Prugniaud, M3 and M7741 strains, with transmission rates of 3 of 8 to 6 of 10 mice inoculated; (4) to determine homologous and heterologous protection. Homologous protection was demonstrated with Prugniaud cysts, and heterologous protection was found between ME-49 and M3 cysts. This finding is consistent with the uniform natural protection against congenital toxoplasmosis seen in immune women and ewes.

Animals↗

PubMed2006

Influence of grain processing on acid-base balance in feedlot steers.

Grain processing (e.g. grinding, steaming, pelleting, flaking) has been reported to modify the incidence of ruminal disturbances in feedlot cattle. This study investigated the effects of two grain processing methods widely used in Spanish feedlots (grinding and pelleting) on animal performance, blood acid-base balance, blood electrolyte levels and serum lactate in a 140-day feedlot experiment with double-muscled Belgian Blue steers. The main aim of the study was to evaluate the way in which these two feeds modify blood acid-base balance, which is closely associated with ruminal pH. In light of our results we conclude that the animals that received the pelleted feed showed a more stable acid-base balance over time than those fed a ground feed. Nevertheless, higher levels of L-lactate and lower base excess (BE) and HCO(3)(-) values for cattle fed pelleted grain reflect a greater risk of grain-acid overload.

Acid-Base Equilibrium↗

PubMed2006

Effect of type and level of fish oil supplementation on yolk fat composition and n-3 fatty acids retention efficiency in laying hens.

1. Laying hen performance and yolk fat fatty acid (FA) concentrations were evaluated with respect to the inclusion in the diet of different sources and levels of marine fish oil (MFO). 2. Twelve diets were arranged factorially, with three sources (MFO1, MFO2_EPA, MFO3_DHA) and four levels of inclusion (15, 30, 45 and 60 g/kg) of MFO. 3. Type of diet had little effect on egg production traits, although laying rate and shell thickness slightly decreased at the highest level of MFO supplementation. 4. An increase in level of inclusion of MFO from 15 to 60 g/kg linearly increased concentrations of C20:5 n-3, C22:5 n-3, C22:6 n-3 and total n-3 FA in yolk fat, but greatly impaired their efficiencies of deposition (g retained/g ingested). 5. An interaction between type and dietary concentration of MFO was found, as the reduction in efficiency of retention of n-3 FA in egg fat with level of MFO was less when the proportion of n-3 in total FA decreased or when that of DHA in total n-3 FA increased. 6. MFO3_ DHA was more efficiently used for total n-3 FA yolk deposition than MFO2_EPA at a similar total n-3 FA intake. 7. Dietary inclusion of MFO reduced LC n-6 FA yolk fat content, which additionally decreased the ratio between total n-6 and total n-3 FA in egg fat. 8. Regression equations were calculated in order to predict efficiency of retention and n-3 FA concentration of yolk fat in the range of diets studied.

Animal Feed↗

PubMed2005

Toxoplasma gondii: partial cross-protection among several strains of the parasite against congenital transmission in a rat model.

Rats were immunized with cysts of two Toxoplasma strains or with RH strain tachyzoites prior to pregnancy. The litters of the 13 rats that received homologous challenges with cysts during pregnancy, were all protected, whereas of 173 rats that received heterologous challenges with cysts or oocysts, only 21 protected their litters. 38.3 and 17% of rats immunized with the RH and with complete strains respectively, and 57% of control rats challenged with cysts, transmitted the infection congenitally. The percentages when similar groups were challenged with oocysts, were 33.3, 48.2, and 56.2%, respectively. Immunization with cysts did not completely protect against challenge with oocysts, even if the same strain was used. The divergence of these results from the complete protection against congenital toxoplasmosis observed in immune women and ewes, might be due to the use of excessive challenge doses in the model.

Animals↗

PubMed2005

Genotoxic effects in a population of nurses handling antineoplastic drugs, and relationship with genetic polymorphisms in DNA repair enzymes.

BACKGROUND: Concern about the genotoxic risk associated with chronic handling of antineoplastic drugs has increased, and usual safety practices may not avoid exposure. METHODS: Comet assay and MN test were performed on 30 oncology nurses and 22 controls. Genetic polymorphisms of XRCC1, XRCC3, and APE1 genes were determined by PCR-RFLP. RESULTS: Data obtained showed increased cytogenetic and DNA damage in the exposed group, although statistical significance was only reached in the comet assay. Significant differences in TL were observed for carriers of the variant alleles of every gene analyzed. However, no significant effect was detected in the MN test. CONCLUSIONS: Evidence that the present handling practices of antineoplastic drugs in some Portuguese hospitals are not enough to prevent exposure are provided. Present data suggest that genetic polymorphisms in the studied DNA repair enzymes may influence the individual susceptibility to DNA damage related to chronic handling of antineoplastic drugs.

Adult↗

PubMed2005

Effect of C content on the mechanical properties of solution treated as-cast ASTM F-75 alloys.

The mechanical properties of solution treated ASTM F-75 alloys with various carbon contents have been studied. Alloys cast under the same conditions were subjected to solution treatment for several periods and then their tensile properties were evaluated. In the as-cast conditions, the alloys exhibited higher strength values with increasing carbon content whereas their ductility was not significantly affected. For the solution treated alloys, the variation of the strength was characterized by a progressive increase for short treatment times until a maximum value was achieved, which was followed by a diminution in this property for longer treatment times. This behavior was more accentuated for the case of the alloys with medium carbon contents, which also exhibited the highest values of strength. Furthermore, the alloy's ductility was enhanced progressively with increasing solution treatment time. This improvement in ductility was significantly higher for the medium carbon alloys compared with the rest of the studied alloys. Thus, high and low carbon contents in solution treated ASTM F-75 alloys did not produced sufficiently high tensile properties.

Alloys↗

PubMed2005

Effects of dietary conjugated linoleic acid and high-oleic sunflower oil on performance and egg quality in laying hens.

(1) Laying hen performance, yolk fatty acid (FA) concentrations, sensory quality and firmness of eggs were evaluated with respect to the inclusion in the diet of conjugated linoleic acid (CLA) and high-oleic acid sunflower oil (HOSO). (2) Nine diets were arranged factorially, with three concentrations of CIA (0, 1 and 2 g/kg) and HOSO (10, 20 and 30 g/kg). (3) Type of diet did not affect egg production traits. (4) Dietary addition of CLA decreased yolk lipid content and yolk lipid concentrations of monounsaturated FA, C(20:4 n-6) and C(22:6 n-3), but increased those of CLA and saturated FA. (5) Dietary addition of HOSO increased monounsaturated FA concentrations in the yolk lipid but decreased those of CLA and saturated FA. (6) CLA supplementation increased yolk moisture and firmness and impaired the sensory quality of eggs. (7) An interaction between CLA and HOSO addition was found as effects of CLA addition on yolk lipid CLA concentrations and egg quality traits were smaller when the amount of HOSO in the diet increased. (8) Regression equations have been calculated in order to predict yolk CLA and C(18:1), concentration from dietary composition, and yolk firmness from yolk FA composition.

Animal Feed↗

PubMed2005

Origin and evolution of Mytilus mussel satellite DNAs.

A phylogenetic reconstruction based on the amplification of 3 satellite DNAs (stDNAs) was carried out in 1 crustacean species and 15 bivalve species of the subclass Pteriomorphia (10, subfamily Mytilinae; 1, subfamily Litophaginae; 1, subfamily Modiolinae, all belonging to family Mytilidae; 1, family Arcidae; and 2, family Pectinidae). The sequences obtained showed motifs with high similarity to those of A and B boxes of tRNA promoter regions. Dot-blot hybridizations revealed that the 3 stDNAs are present mainly in high copy numbers for each species of the genus Mytilus, whereas for the other species they appear in low copy numbers. Maximum-parsimony trees evidenced a tendency to group Mytilus clones together, and species containing these sequences as a single copy were distributed among the different mytilids. Finally, the possible origin and evolution of these stDNAs is discussed.

Animals↗

PubMed2005

Effects of all-trans retinoic acid on tumor recurrence and metastasis.

OBJECTIVE: All-trans-retinoic acid (ATRA) promotes cell differentiation. We have studied its effect on the local recurrence and metastatic spreading of an experimental rhabdomyosarcoma in rats. DESIGN: syngenic rhabdomyosarcoma cells (S4MH) were inoculated s.c. in male WAG/RijCrl rats. After 25 days tumors were excised and a 40% hepatectomy was performed for all animals. Ten days later the rats were sacrificed and a thorough necropsy was performed. The animals were randomly allocated to receive daily doses of ATRA (5 mg/kg, i.p.) or its solvent (Clinoleic/ethanol 90/10), starting three days before surgery until the end of the experiment. RESULTS: ATRA reduced the incidence of local recurrence from 70 to 33% (p < 0.05), but the tumor size was not altered (1.8 vs. 2.0 cc). Regarding inguinal metastasis, there was a six-fold decrease (0.2 vs. 1.2 cc; p < 0.05) in mean tumor volume, although the rate of this proliferation increased sharply (86 vs. 29%; p < 0.05) for treated animals. The volume of the retroperitoneal tumor masses also decreased with ATRA (0.7 vs. 5.1 cc; p < 0.05), but the difference in rate was not significant (71 vs. 67%). Lung metastases, which were present in 100% of control animals, were found in only 33% of treated rats, while the mean number of metastatic foci dropped from 26.7 to 5.7 (p < 0.05). CONCLUSION: Protocols including retinoid administration prior to and following primary tumor excision could help in controlling both recurrence and metastatic progression in surgically treated rhabdomyosarcoma.

Animals↗

PubMed2004

Chromosome analysis and mapping of ribosomal genes by one- and two-color fluorescent in situ hybridization in Hinnites distortus (Bivalvia: Pectinidae).

Metaphase chromosomes of the scallop Hinnites distortus were analyzed using Giemsa staining, chromosome measurements, silver staining, one- and two-color fluorescent in situ hybridization (FISH) ribosomal DNA (rDNA) probes, and 4',6-diamidino-2-phenylindole (DAPI) banding compatible with in situ hybridization. The karyotype (2n = 38) consists of three submetacentric-metacentric, one submetacentric, one subtelocentric-submetacentric, and 14 subtelocentric pairs. The 18S-28S rDNA maps at the centromeric level of two subtelocentric pairs, but not more than two nucleolus organizer region (NOR)-bearing chromosomes were transcriptionally active. The 5S rDNA seems to show a conventional tandem arrangement with a repeat unit of about 450 bp and it maps at the pericentromeric region of the long arm of one subtelocentric pair. Two-color FISH demonstrated that 18S-28S rDNA and 5S rDNA are not syntenic. Sequential FISH/Giemsa staining and subsequent chromosome pairing allow us to propose that pairs 9 and 12 carry the 18S-28S rDNA and pair 13 carries the 5S rDNA. All chromosomes are characterized as containing constitutive heterochromatin at the centromeric region. The data provided are the first contribution toward construction of the molecular karyotype of H. distortus and will be useful in assessing evolutionary relationships within scallops.

Animals↗

PubMed2004

Photocatalytic degradation of formaldehyde containing wastewater from veterinarian laboratories.

The photocatalytic destruction of methanol, formaline (mixture of formaldehyde, methanol and water) and formaline wastes from the preservation of vertinarian physiologic samples has been attempted by two different processes, at high concentrations of reagents and by dossification of reagents, varying pH in both. Experiment evolution has been monitored by measuring the organic matter such as TOC and formaldehyde concentrations [H2CO]. Also, methanol and methanol-formaldehyde interactions with the TiO2 surface have been analysed by FTIR spectroscopy. Results indicate that at high concentrations the catalyst surfacial alterations given by methoxy, formates or carbonates, according to the pH of the sample can profoundly affect catalyst behaviour. It has been established that reagent dossification is advantageous for enhancing photonic efficiency as it minimizes the adsorbate presence that hampers the photocatalytic process.

Carbon↗

PubMed2004

Effects of dietary conjugated linoleic acid and fish oil supplementation on performance and egg quality in laying hens.

1. Laying hen performance, yolk fat fatty acid concentrations and firmness of eggs were evaluated with respect to the inclusion in the diet of conjugated linoleic acid (CLA) and fish oil. 2. Nine diets were arranged factorially, with three levels of supplementation of CLA (1, 3 and 5 g/kg) and fish oil (0, 14 and 20 g/kg). 3. Type of diet did not affect egg production traits. 4. CLA addition increased yolk weight and yolk fat concentrations of CLA, saturated and total long-chain n-3 fatty acids, but decreased those of monounsaturated and total long-chain n-6 fatty acids. 5. Fish oil addition increased long-chain n-3 fatty acids yolk fat concentrations but decreased those of CLA, saturated and long-chain n-6 fatty acids. 6. Effects of CLA addition on yolk fat concentrations of C22:4 n-6 and C20:5 n-3 were greater when no fish oil was added to the diet. 7. CLA supplementation increased linearly yolk moisture and firmness and altered albumen and yolk pH.

Animal Feed↗

PubMed2003

Cytogenetics of the razor clam Solen marginatus (Mollusca: Bivalvia: Solenidae).

The razor clam Solen marginatus has a diploid chromosome number of 38. The karyotype consists of one metacentric/submetacentric, three submetacentric/metacentric, five submetacentric, one submetacentric/subtelocentric, one subtelocentric/submetacentric, six subtelocentric and two telocentric chromosome pairs. Staining with chromomycin A3 revealed bright positive bands subcentromerically in the long arms of one medium-sized subtelocentric pair, while DAPI staining showed uniform fluorescence in all chromosomes of the complement. Fluorescence in situ hybridization using an 18S-5.8S-28S rDNA probe locates these loci at the subcentromeric region of one subtelocentric pair and at the subtelomeric region of another subtelocentric pair.

Animals↗

PubMed2003

[Effect of hepatic resection on development of liver metastasis].

In the early stages of metastasis, development of the disease is dependent on growth factors produced by the host. There are clinical situations associated with an increase in these factors, such as partial resection of metastasized liver. Given the important role of hepatotrophic factors in liver regeneration, we have studied the effect of partial hepatectomy on the development of residual micrometastases in the liver, and on the neoplastic process as a whole. We used a murine model in which a rabdomiosarcoma was established by subcutaneous inoculation of syngeneic tumor cells in male Wag rats. Subsequently, the primary tumor was resected and/or a 40% hepatectomy was performed. The effect of these two surgical procedures on the tumor process was analyzed on the 25th and 35th days post-inoculation, and the percentage of regenerating hepatocytes was assessed. Both the tumorectomy and liver resection, when not combined, produced an increase in regional adenopathies without modifying the evolution of metastasis in the liver. However, when tumor excision and partial hepatectomy were performed simultaneously, there was a net increase in the metastatic process. In addition to a rapid spread of the disease (lung, mediastinum, retroperitoneum), the number of liver metastases increased by 300%. This development coincided with a steep rise in the percentage of regenerating hepatocytes, which nearly doubled that of the group subjected only to liver resection. We conclude that liver resection, alone or combined with excision of the primary tumor, may enhance tumor progression, both locally and at the metastasic level.

Animals↗

PubMed2002

Phenological behaviour of Quercus in Ourense (NW Spain) and its relationship with the atmospheric pollen season.

Knowing the beginning of the pollen season is of particular importance to people allergic to a given pollen. Phenological studies in combination with aerobiological studies enable us to observe the relationship between the reproductive phenology of the species and their airborne pollen curves. They also enable us to study the relationship between the release of pollen from anthers and its presence in the atmosphere. The objectives of this study are (1) to determine chill and heat requirements for different phenological phases in the Quercus species present in Ourense (Spain), (2) to verify the synchronization between the flowering event and the presence of Quercus pollen in the air, (3) to select the best criterion for determining the onset of the pollen season according to phenological data, and finally, (4) to obtain models enabling us to determine the onset of the pollen season. Pollen monitoring was carried out from 1993 to 2001, by means of a 7-day Lanzoni VPPS pollen trap and, in order to characterize the floral phenophase of different Quercus species, a sampling method was applied from February to June 2001. We observed that climatic and biotic factors can produce a delay in the onset of the pollen season. Temperatures above 8 degrees C and between 6 degrees C to 8 degrees C are good threshold temperatures for estimating chill and heat requirements respectively. Medium-distance transportation of Quercus robur and Quercus pyrenaica pollen from areas 10-30 km away influences the concentrations of Quercus pollen registered in Ourense.

Allergens↗

PubMed2002

Identification of four scallop species using PCR and restriction analysis of the ribosomal DNA internal transcribed spacer region.

Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis of the ribosomal DNA region spanning the 5.8S RNA gene and the 2 flanking internal transcribed spacers (ITSs) was performed to establish DNA-based molecular markers for the identification of the scallops Aequipecten opercularis, Chlamys distorta, Mimachlamys varia, and Pecten maximus. Chlamys distorta was distinguished simply by ITS size. Species-specific restriction patterns were found with the restriction enzyme AluI, and also with SmaI for A. opercularis and M. varia. When ITS sizes and the RFLPs obtained with SmaI were combined, the 4 scallops were also differentiated. Additional species-specific RFLPs were revealed after ITS-2 PCR amplification and subsequent digestion with Hsp92II. Using this marker, canned scallops were identified. Thus this work provides a simple, reliable, and rapid method for the identification of scallops that can be used when species-specific morphologic characteristics are removed or when specimens are small in size.

Journal Article↗

PubMed2002

Effect of vitamin E and A supplementation on egg yolk alpha-tocopherol concentration.

The objective of this study was to asses the effect of dietary dl-alpha-tocopheryl acetate (alpha-TAC) and vitamin A supplementation on egg yolk alpha-tocopherol (alpha-T) concentration. A total of 96 ISA brown hens (a brown-egg laying hen), 32 wk of age, was used. Eight concentrations of alpha-TAC (0, 20, 40, 80, 160, 320, 640, and 1,280 IU/kg diet) were included in a corn-soybean meal-based diet containing 4,000 IU of vitamin A/kg diet. Production parameters were not affected by dietary treatment. Interhen variation in yolk alpha-T concentration increased at higher dietary intakes. Logarithmic transformation stabilized variance and showed the existence of a linear relationship between dietary alpha-TAC supplementation level and alpha-T egg yolk concentration (P < 0.001). As the dietary concentration of alpha-TAC rose, efficiency of uptake of alpha-T from feed to yolk decreased linearly (P < 0.001). A parallel experiment was carried out in which four additional groups of hens were fed diets containing four levels of dietary alpha-TAC (0, 40, 160, and 640 IU/kg) and 40,000 IU vitamin A/kg diet. A significantly lower egg yolk alpha-T concentration was found in hens fed diets including the highest level of vitamin A supplementation (P < 0.001). No interaction of dietary alpha-TAC and vitamin A concentrations was observed on egg yolk alpha-T concentration. No effect of dietary treatment was observed on yolk oxidation and other egg quality characteristics.

Animals↗