Estudi epidemiològic de l'obesitat de 1r d'ESO de l'IES Pedraforca

Treball de recerca realitzat per una alumna d'ensenyament secundari i guardonat amb un Premi CIRIT per fomentar l'esperit científic del Jovent l'any 2009. L'obesitat és una malaltia crònica que es caracteritza per un augment de la massa grassa i en conseqüència per un augment de pes. En el segle XXI aquesta malaltia, considerada epidèmia, està arribant a la població infantil i adolescent, i ha cridat l'atenció de totes les institucions de salut pública que estan lluitant per evitar aquesta alta prevalença d'obesitat i sobrepès. Aquest estudi confirma que existeix un alt percentatge d'obesitat i sobrepès en l'edat infantil i que està relacionat amb factors de risc (alguns modificables) que poden ser clau per a evitar aquesta malaltia. El mètode emprat és la realització d’un estudi epidemiològic transversal sobre una mostra de nens compresa en 39 individus de 12 a 14 anys d'edat. Es van determinar el pes, la talla, el plec bicipital i tricipital, l'ample del canell i del colze, a més de la realització d'una enquesta sobre hàbits alimentaris en l’esmorzar i dades socioculturals. L'obesitat i el sobrepès es van definir com resultats de IMC iguals als percentils 85 i 97 de les taules Orbegozo, respectivament. Els resultats van mostrar una prevalença de sobrepès i obesitat en la nostra mostra de població que va ser de 28,2%, la de només sobrepes del 15,4% i la de només obesitat del 12,8%. La prevalença d'obesitat és major en nens amb un 13,6% que en nenes 12,5% igual que el sobrepès. L'obesitat i sobrepès és major quan els estudis materns són inferiors als universitaris, també quan existeixen famílies amb 3 o més fills i quan es veu la TV més de 3 hores al dia.

Parents, television and cultural change

This paper develops a model of cultural transmission where television plays a central role for socialization. Parents split their free time between educating their children which is costly and watching TV which though entertaining might socialize the children to the wrong trait. The free to air television industry maximizes advertisement revenue. We show that TV watching is increasing in cultural coverage, cost of education, TV's entertainment value and decreasing in the perceived cultural distance between the two traits. A monopolistic television industry captures all TV watching by both groups if the perceived cultural distance between groups is small relative to the TV's entertainment value. Otherwise, more coverage will be given to the most profitable group where profitability increases in group size, advertisement sensitivity and perceived cultural distance. This leads to two possible steady states where one group is larger but both groups survive in the long run. Competition in the media industry might lead to cultural extinction but only if one group is very insensitive to advertisement and not radical enough not to watch TV. We briefly discuss the existing evidence for the empirical predictions of the model.

Vitalidad etnolingüística, medios de comunicación e identidad étnica. Un estudio con grupos indígenas de Chiapas

Aquest estudi representa la primera exploració de l'ús de la televisió i la selecció de programes per part de grups d'indígenes a Chiapas. Més concretament, s'examina com els membres d'aquests grups seleccionen canals i programes específics dels mitjans de comunicació per raons d'etnicitat, i com això té a veure amb estratègies de mobilitat social. Les dades de 173 indígenes estudiants de la universitat Intercultural de Chiapas van indicar que per a 77 membres d'aquesta mostra, veure la televisió i seleccionar programes sobre la base de la seva etnicitat és una activitat de visualització important per a la seva autoestima etnolingüística. Aquests resultats es discuteixen en termes de la representació televisiva dels grups ètnics de Chiapas i motiven la realització de futures investigacions sobre aquests temes a Chiapas.

δ15N value does not reflect fasting in mysticetes.

The finding that tissue δ15N values increase with protein catabolism has led researchers to apply this value to gauge nutritive condition in vertebrates. However, its application to marine mammals has in most occasions failed. We investigated the relationship between δ15N values and the fattening/fasting cycle in a model species, the fin whale, a migratory capital breeder that experiences severe seasonal variation in body condition. We analyzed two tissues providing complementary insights: one with isotopic turnover (muscle) and one that keeps a permanent record of variations in isotopic values (baleen plates). In both tissues δ15N values increased with intensive feeding but decreased with fasting, thus contradicting the pattern previously anticipated. The apparent inconsistency during fasting is explained by the fact that a) individuals migrate between different isotopic isoscapes, b) starvation may not trigger significant negative nitrogen balance, and c) excretion drops and elimination of 15N-depleted urine is minimized. Conversely, when intensive feeding is resumed in the northern grounds, protein anabolism and excretion start again, triggering 15N enrichment. It can be concluded that in whales and other mammals that accrue massive depots of lipids as energetic reserves and which have limited access to drinking water, the δ15N value is not affected by fasting and therefore cannot be used as an indicatior of nutritive condition.

Stable isotopes indicate population structuring in the Southwest Atlantic population of right whales

From the early 17th century to the 1970s southern right whales, Eubalaena australis, were subject to intense exploitation along the Atlantic coast of South America. Catches along this coast recorded by whalers originally formed a continuum from Brazil to Tierra del Fuego. Nevertheless, the recovery of the population has apparently occurred fragmentarily, and with two main areas of concentration, one off southern Brazil (Santa Catarina) and another off central Argentina (Peninsula Valdés). This pattern suggests some level of heterogeneity amongst the population, which is apparently contradicted by records that traced individuals moving throughout the whole geographical extension covered by the species in the Southwest Atlantic. To test the hypothesis of the potential occurrence of discrete subpopulations exploiting specific habitats, we investigated N, C and O isotopic values in 125 bone samples obtained from whaling factories operating in the early 1970s in southern Brazil (n = 72) and from contemporary and more recent strandings occurring in central Argentina (n = 53). Results indicated significant differences between the two sampling areas, being δ13C and δ18O values significantly higher in samples from southern Brazil than in those from central Argentina. This variation was consistent with isotopic baselines from the two areas, indicating the occurrence of some level of structure in the Southwest Atlantic right whale population and equally that whales more likely feed in areas commonly thought to exclusively serve as nursing grounds. Results aim at reconsidering of the units currently used in the management of the southern right whale in the Southwest Atlantic Ocean. In the context of the current die-off affecting the species in Peninsula Valdés, these results also highlight the necessity to better understand movements of individuals and precisely identify their feeding areas.

δ15N value does not reflect fasting in mysticetes.

The finding that tissue δ15N values increase with protein catabolism has led researchers to apply this value to gauge nutritive condition in vertebrates. However, its application to marine mammals has in most occasions failed. We investigated the relationship between δ15N values and the fattening/fasting cycle in a model species, the fin whale, a migratory capital breeder that experiences severe seasonal variation in body condition. We analyzed two tissues providing complementary insights: one with isotopic turnover (muscle) and one that keeps a permanent record of variations in isotopic values (baleen plates). In both tissues δ15N values increased with intensive feeding but decreased with fasting, thus contradicting the pattern previously anticipated. The apparent inconsistency during fasting is explained by the fact that a) individuals migrate between different isotopic isoscapes, b) starvation may not trigger significant negative nitrogen balance, and c) excretion drops and elimination of 15N-depleted urine is minimized. Conversely, when intensive feeding is resumed in the northern grounds, protein anabolism and excretion start again, triggering 15N enrichment. It can be concluded that in whales and other mammals that accrue massive depots of lipids as energetic reserves and which have limited access to drinking water, the δ15N value is not affected by fasting and therefore cannot be used as an indicatior of nutritive condition.

Stable isotopes provide insight into population structure and segregation in eastern North Atlantic sperm whales

In pelagic species inhabiting large oceans, genetic differentiation tends to be mild and populations devoid of structure. However, large cetaceans have provided many examples of structuring. Here we investigate whether the sperm whale, a pelagic species with large population sizes and reputedly highly mobile, shows indication of structuring in the eastern North Atlantic, an ocean basin in which a single population is believed to occur. To do so, we examined stable isotope values in sequential growth layer groups of teeth from individuals sampled in Denmark and NW Spain. In each layer we measured oxygen- isotope ratios (δ18O) in the inorganic component (hydroxyapatite), and nitrogen and carbon isotope ratios (δ15N: δ13C) in the organic component (primarily collagenous). We found significant differences between Denmark and NW Spain in δ15N and δ18O values in the layer deposited at age 3, considered to be the one best representing the baseline of the breeding ground, in δ15N, δ13C and δ18O values in the period up to age 20, and in the ontogenetic variation of δ15N and δ18O values. These differences evidence that diet composition, use of habitat and/or migratory destinations are dissimilar between whales from the two regions and suggest that the North Atlantic population of sperm whales is more structured than traditionally accepted.