Calibration of visually estimated distances to migrating seabirds with radar measurements

ABSTRACT Censusing seabirds from coastal areas requires reliable estimates of bird numbers and the distances of the birds from the coastline. Logistical constraints make visual estimation of distances the only feasible method in many studies. We tested the accuracy of visually estimated offshore distances of six migratory seabird species in the Strait of Gibraltar using simultaneous measurements obtained by radar. Most birds (91%) were detected within 3 km of the coast and we truncated our calibration at this distance. We found a strong correlation between radar and visual estimates (R²= 0.83, P < 0.0001). The magnitude of errors in visual estimates was moderate and ranged from 0.08 to 0.20 for different distances and observers. Among the factors potentially affecting the accuracy of visual estimates of distance to seabird in our study were observer identity, bird species, bird behavior, and weather; the most parsimonious model in our study included observer identity as the only predictor, and no model with more than one predictor had a smaller Akaike's information criterion value. Radar can be used to help train observers and to reduce biases in visual estimates of distances by means of calibration. When no other methods are available to accurately measure distances to seabirds, visual estimates of distances, recorded by experienced observers and once calibrated with radar (or other ground‐truthing methods), may be acceptable for different species under a wide range of environmental conditions.     

Expression and purification of polyhistidine-tagged rotavirus NSP4 proteins in insect cells

The rotavirus nonstructural NSP4 protein, a transmembrane endoplasmic reticulum-specific glycoprotein, has been described as the first viral enterotoxin. Purified NSP4 or a peptide corresponding to NSP4 residues 114-135 induces diarrhea in young mice. NSP4 has a membrane-destabilizing activity and causes an increase in intracellular calcium levels and chloride secretion by a calcium-dependent signalling pathway in eucaryotic cells. In this study, four recombinant baculoviruses were generated expressing the rotavirus NSP4 glycoprotein from the human strains Wa and Ito, the porcine strain OSU, and the simian strain SA11, which belong to two different NSP4 genotypes, A and B. The recombinant glycoproteins, expressed as polyhistidine-tagged molecules, were analyzed by Western blotting and immunoprecipitation. Newborn mice responded with diarrhea after inoculation with each of the recombinant NSP4 proteins.     

DNA damage in female workers exposed to pesticides in banana plantations at Limón,Costa Rica

Pesticide use in Costa Rica is very high and all year round. A high percentage of what is sprayed remains in the environment and in the living organisms around. This situation brings contamination and health problems to people in contact with them. The onset of adverse effects may be in the short or the long term, and symptoms vary widely, from headaches to cancer. Much research in this area has been devoted to acute or chronic effects, and not until recently to the genotoxic effect of pesticides. This study evaluated the genotoxic effect of pesticides used in banana packing activities, using the comet assay (single cell electrophoresis) as the biological marker in lymphocytes. This was a case-control double blind study of 30 exposed women from 15 banana farms and 28 women not occupationally exposed to pesticides from the same geographic area. Results show damage to single stranded DNA after working from 5 to 15 years (R2 = 0.12). In Costa Rica we do not have an historical record of the kind of pesticides used in banana farms, the period of time and for how long were they used. This prevented further analysis concerning dose, frequency of exposure and use of new or old kind of pesticides in the farms in relation to DNA damage. The comet assay is of value in the genetic monitoring of pesticide exposed populations.     

Effects of climatic variability on the annual carbon sequestration by a boreal aspen forest

To evaluate the carbon budget of a boreal deciduous forest, we measured CO₂ fluxes using the eddy covariance technique above an old aspen (OA) forest in Prince Albert National Park, Saskatchewan, Canada, in 1994 and 1996 as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). We found that the OA forest is a strong carbon sink sequestering 200 ± 30 and 130 ± 30 g C m^–2 y^–1 in 1994 and 1996, respectively. These measurements were 16–45% lower than an inventory result that the mean carbon increment was about 240 g C m^–2 y^–1 between 1919 and 1994, mainly due to the advanced age of the stand at the time of eddy covariance measurements. Assuming these rates to be representative of Canadian boreal deciduous forests (area ≈ 3 × 10⁵ km²), it is likely they can sequester 40–60 Tg C y^–1, which is 2–3% of the missing global carbon sink. The difference in carbon sequestration by the OA forest between 1994 and 1996 was mainly caused by the difference in leaf emergence date. The monthly mean air temperature during March–May 1994, was 4.8 °C higher than in 1996, resulting in leaf emergence being 18–24 days earlier in 1994 than 1996. The warm spring and early leaf emergence in 1994 enabled the aspen forest to exploit the long days and high solar irradiance of mid-to-late spring. In contrast, the 1996 OA growing season included only 32 days before the summer solstice. The earlier leaf emergence in 1994 resulted 16% more absorbed photosynthetically active radiation and a 90 g C m^–2 y^–1 increase in photosynthesis than 1996. The concomitant increase in respiration in the warmer year (1994) was only 20 g C m^–2 y^–1. These results show that an important control on carbon sequestration by boreal deciduous forests is spring temperature, via the influence of air temperature on the timing of leaf emergence.     

Electron microscope analysis of the E polytene chromosome of Drosophila subobscura: region 70B to 72D

Revision of the reference map of the polytene chromosomes of Drosophila subobscura was started by means of the electron microscope. We present a map of regions 70B to 72D of the E chromosome obtained from squashed and thin-sectioned salivary glands. It was observed that the total number of bands in divisions 70B to 72D is considerably higher than those depicted in the reference map of Kunze-Mühl and Müller. Functional considerations are made of some regions that show puff structures.     

Developmental regulation of calcium-dependent feedback in Xenopus rods

The kinetics of activation and inactivation in the phototransduction pathway of developing Xenopus rods were studied. The gain of the activation steps in transduction (amplification) increased and photoresponses became more rapid as the rods matured from the larval to the adult stage. The time to peak was significantly shorter in adults (1.3 s) than tadpoles (2 s). Moreover, adult rods recovered twice as fast from saturating flashes than did larval rods without changes of the dominant time constant (2.5 s). Guanylate cyclase (GC) activity, determined using IBMX steps, increased in adult rods from approximately 1.1 s(-1) to 3.7 s(-1) 5 s after a saturating flash delivering 6,000 photoisomerizations. In larval rods, it increased from 1.8 s(-1) to 4.0 s(-1) 9 s after an equivalent flash. However, the ratio of amplification to the measured dark phosphodiesterase activity was constant. Guanylate cyclase-activating protein (GCAP1) levels and normalized Na+/Ca2+, K+ exchanger currents were increased in adults compared with tadpoles. Together, these results are consistent with the acceleration of the recovery phase in adult rods via developmental regulation of calcium homeostasis. Despite these large changes, the single photon response amplitude was approximately 0.6 pA throughout development. Reduction of calcium feedback with BAPTA increased adult single photon response amplitudes threefold and reduced its cutoff frequency to that observed with tadpole rods. Linear mathematical modeling suggests that calcium-dependent feedback can account for the observed differences in the power spectra of larval and adult rods. We conclude that larval Xenopus maximize sensitivity at the expense of slower response kinetics while adults maximize response kinetics at the expense of sensitivity.     

Chromosomic aberrations in female workers exposed to pesticides

The purpose of this work was to determine if the occupational exposure to those pesticides used at banana plantations' packaging plants produces genetic damage to somatic cells of female workers. Chromosomal aberrations were scored in lymphocytes of 20 women, 10 female exposed workers and 10 female controls. Workers were recruited from independent farms from two locations in Costa Rica, during January through June in 1996 and 1997. These females had a minimum of three months of work, had never received chemotherapy or radiotherapy and did some of these labors: sealing, spraying or weighting of bananas. Control unexposed females lived in the same area, were of similar age and neither them nor their husbands/mates had ever worked in pesticide related labors. For each female, 100 mitotic figures were scored. The kind of aberrations detected were acentric fragments, dicentric chromosomes, rings, gaps and breaks. Among workers, 16% of cells (n=1000) had one or more abnormalities, whereas control unexposed females had 6% of cells (n=1000) with comparable anomalies (p < 0.05). In conclusion, the pesticide exposure is a risk factor for chromosome aberrations in female somatic cells.     

Arbuscular mycorrhizas in coastal sand dunes of the Paraguaná Peninsula, Venezuela

Arbuscular mycorrhizal colonization was measured in the most abundant plant species of the Paraguaná Peninsula, northwestern Venezuela. These plant species included: Acacia tortuosa, Argusia gnaphalodes, Croton punctatus, Croton rhamnifolius, Egletes prostrata, Melochia tomentosa, Panicum vaginatum, Scaevola plumieri, Sporobolus virginicus, Suriana maritima, Leptothrium rigidum, and Fimbristylis cymosa. Mycorrhizal colonization was assessed using the Trouvelot et al. (1986) method that allows for simultaneous evaluation of frequency of colonization (%F), intensity of colonization (%M), and the proportion of arbuscules (%A) and vesicles (%V) present in the roots. Average frequency of colonization was 69%. The highest frequency of colonization was around 92% in C. rhamnifolius and A. tortuosa; in the other species, it varied from 49 to 86%. L. rigidum and F. cymosa were considered nonmycorrhizal because its colonization was very scarce and at all times appeared without arbuscules. Average intensity of colonization was 7%. The highest intensity of colonization was 18% in C. rhamnifolius. In the other species, it varied from 3 to 15%. Paspalum vaginatum, A. gnaphalodes, M. tomentosa, and S. maritima had their fungal structures tightly packed in modified little ovoid roots. In general, frequency of AM colonization was high and similar to those reported for other tropical ecosystems, whereas the intensity of AM colonization was low and similar to values obtained in analogous studies in disturbed ecosystems.     

Association of the p53 codon 72 polymorphism to gastric cancer risk in a hight risk population of Costa Rica

Gastric cancer is the second most common cancer associated death cause worldwide. Several factors have been associated with higher risk to develop gastric cancer, among them genetic predisposition. The p53 gene has a polymorphism located at codon 72. which has been associated with higher risk of several types of cancer, including gastric cancer. The aim of this study was to determine the association of p53, codon 72 polymorphism. with the risk of gastric cancer and pre-malignant lesions in a high-risk population from Costa Rica. The genotyping was carried out by PCR-RFLP in 58 gastric cancer patients, 99 controls and 41 individuals classified as group I or II. according to the Japanese histological classification. No association was found for p53. codon 72 polymorphism with neither the risk of gastric cancer nor the risk of less severe gastric lesions in the studied population. Based on this study and taking into account other studies carried out with p53, codon 72 polymorphism. the role of this polymorphismn in the development of gastric cancer remains unclear. De novo mutations on p53 gene produced during neoplasic development of this disease might play a greater role than germinal polymorphisms of the gene. Other polymorphic genes have been associated with higher risk to develop gastric cancer.