Biomedical subjects

Carlos Navarro

Publications and source records attributed to Carlos Navarro.

5 recordsLinked to original sources

PubMed2004

Malarial parasites decrease reproductive success: an experimental study in a passerine bird.

Malarial parasites are supposed to have strong negative fitness consequences for their hosts, but relatively little evidence supports this claim due to the difficulty of experimentally testing this. We experimentally reduced levels of infection with the blood parasite Haemoproteus prognei in its host the house martin Delichon urbica, by randomly treating adults with primaquine or a control treatment. Treated birds had significantly fewer parasites than controls. The primaquine treatment increased clutch size by 18%; hatching was 39% higher and fledging 42% higher. There were no effects of treatment on quality of offspring, measured in terms of tarsus length, body mass, haematocrit or T-cell-mediated immune response. These findings demonstrate that malarial parasites can have dramatic effects on clutch size and other demographic variables, potentially influencing the evolution of clutch size, but also the population dynamics of heavily infected populations of birds.

Animals↗

PubMed2004

Double gametocyte infections in apicomplexan parasites of birds and reptiles.

The simultaneous occurrence of male and female gametocytes inside a single host blood cell has been suggested to enhance apicomplexan transmission ["double gametocyte infection (DGI) hypothesis"]. We did a bibliographic search and a direct screen of blood smears from wild birds and reptiles to answer, for the first time, how common are these infections in the wild. Taking these two approaches together, we report here cases of DGIs in Plasmodium, Haemoproteus, Leucocytozoon and Hepatozoon, and cases of male-female DGIs in Haemoproteus of birds and reptiles and in Leucocytozoon of birds. Thus, we suggest that DGIs and male female DGIs are more widespread than previously thought, opening a new research avenue on apicomplexan transmission.

Animals↗

PubMed2003

Genetic structure of Mesoamerican populations of Big-leaf mahogany (Swietenia macrophylla) inferred from microsatellite analysis.

While microsatellites have been used to examine genetic structure in local populations of Neotropical trees, genetic studies based on such high-resolution markers have not been carried out for Mesoamerica as a whole. Here we assess the genetic structure of the Mesoamerican mahogany Swietenia macrophylla King (big-leaf mahogany), a Neotropical tree species recently listed as endangered in CITES which is commercially extinct through much of its native range. We used seven variable microsatellite loci to assess genetic diversity and population structure in eight naturally established mahogany populations from six Mesoamerican countries. Measures of genetic differentiation (FST and RST) indicated significant differences between most populations. Unrooted dendrograms based on genetic distances between populations provide evidence of strong phylogeographic structure in Mesoamerican mahogany. The two populations on the Pacific coasts of Costa Rica and Panama were genetically distant from all the others, and from one another. The remaining populations formed two clusters, one comprised of the northern populations of Mexico, Belize and Guatemala and the other containing the southern Atlantic populations of Nicaragua and Costa Rica. Significant correlation was found between geographical distance and all pairwise measures of genetic divergence, suggesting the importance of regional biogeography and isolation by distance in Mesoamerican mahogany. The results of this study demonstrate greater phylogeographic structure than has been found across Amazon basin S. macrophylla. Our findings suggest a relatively complex Mesoamerican biogeographic history and lead to the prediction that other Central American trees will show similar patterns of regional differentiation.

Central America↗

PubMed2002

The tree Cedrela odorata (Meliaceae): a morphologically subdivided species in Costa Rica.

In Latin America. Cedrela odorata is a wide ranging species that occurs in several environments, where it shows significant morphological variation. A common garden experiment was established with seedlings from 63 families of ten populations from two habitat types (mesic and dry), distributed throughout Costa Rica, to examine the relationships between quantitative variation and site of population origin. Seedlings from dry areas tended to be distinct from those from mesic areas, with climatic grouping of provenance explaining a mean of 52% of the total variance and 80% of the genetic variance. Cluster analysis for seedling traits showed two natural groupings of families, which corresponded for the most part with the regional population groupings into mesic (Atlantic and South Pacific) and dry (North Pacific) groups. Cluster analysis based on seed weight and size also separated populations into mesic and dry climatic groups. Seeds from populations in dry areas were 43% heavier, and seedlings were 61% taller, 117% greater in diameter, and with leaflets 39% longer and 81% wider. These differences may be related to fast growth in the dry zone for taking advantage of early life cycle moisture availability. These findings may indicate incipient speciation in C. odorata in Costa Rica. Evaluation of reproductive isolating mechanisms between populations from the mesic and dry zones, and of clines at potential zones of hybridization would assist in testing a speciation hypothesis.

Analysis of Variance↗

PubMedDate not supplied

Prospective study of resting energy expenditure changes in head and neck cancer patients treated with chemoradiotherapy measured by indirect calorimetry.

OBJECTIVE: The prevalence of malnutrition is high in patients with head and neck cancer due to tumor location and coadjuvant treatment. We studied changes in resting energy expenditure (REE) during treatment with chemoradiotherapy and compared the measured REE by indirect calorimetry (IC) with the value estimated by the Harris-Benedict (HB) formula. METHODS: Eighteen patients with head and neck cancer (15 men and 3 women, mean age 57 +/- 10.7 y, age range 30-71 y) entered the study. All patients were treated with radiotherapy (70.8 +/- 1 Gy, range 70-72) and received 37.4 +/- 3.5 fractions (range 32-42) and concurrent chemotherapy with cisplatinum (absolute doses of 400 to 1000 mg). Nutrition assessment included anthropometry (body mass index, triceps skinfold thickness, subscapular skinfold thickness, midarm circumference, and midarm muscle circumference) and tetrapolar bioimpedance (Holtain BC). The IC (kcal/24 h; Deltatrac II MBM-200) was performed after an overnight fast. Measurements were done before treatment, at weeks 2, 4, and 6 of treatment, at the end of treatment, and 2 wk after treatment. RESULTS: Body mass index decreased during treatment from 24.7 +/- 4.4 kg/m(2) (range 16.9-31.4) to 22.3 +/- 4.2 kg/m(2) (range 15.1-29.6). REE (kcal/24 h) changed significantly during treatment (IC P < 0.05, HB formula P < 0.001). REE measured by IC appeared as a U-shaped curve, but REE estimated by the HB formula decreased during treatment. The HB underestimated REE measurements compared with IC. These differences were statistically significant before treatment, at the end of treatment, and 2 wk after treatment (P < 0.05) and showed a limited clinical agreement with the Bland-Altman method. CONCLUSIONS: REE measured by IC significantly changed during chemoradiotherapy. It was higher before treatment, at the end of treatment, and 2 wk after treatment. The HB formula underestimated REE in these patients. IC is a suitable method for measuring REE in this cohort of patients.

Adult↗