Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time.

Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation - and associated ecosystem consequences - have the potential to be much greater than we have observed to date.

Síndrome de shock tóxico estreptocócico / Streptococcal toxic shock syndrome

El síndrome de shock toxico estreptocócico (SSTE) se ha definido como la presencia de infección invasiva por Estreptococo del grupo A asociada a shock y falla multiorgánica. Presenta una mortalidad entre 30% y 70% de los casos según las series publicadas y se han reportado de 1 a 5 casos por 100000 habitantes. Es una infección rápidamente progresiva que afecta la piel, tejido celular subcutáneo, fascia superficial y ocasionalmente la profunda, puede producir también necrosis hística y severa toxicidad sistémica. Se presenta el caso de un paciente de 15 años de edad con cuadro clínico de 3 días de evolución previa a su hospitalización, caracterizado por dolor y signos de flogosis en fosa iliaca derecha posterior a contusión en dicha región. Presento una evolución tórpida durante sus primeros días de internación con inflamación de tejidos blandos en el lugar de la contusión y dolor asociado a fiebre, escalofríos, malestar general, náuseas, vómitos y diarrea. El dolor se intensifica, la zona de inflamación se convierte en necrótica, finalmente la enfermedad progresa hasta shock tóxico y falla multiorgánica.

Streptococcal toxic shock syndrome (STSS) was be defined as the presence of invasive infection byA group of Estreptococcus, associated to shock and multiorganic failure. It has mortality between 30 and 70 percent according to the publicized series and has been reported from 1 to 5 cases of 100000 inhabitants. It is a rapidly progressive infection that affects the skin, subcutaneous cellular tissue, superficial fascia and occasionally deep tissue, it can also produce hystic necrosis and severe systemic toxicity. We report the case of a 15 year-old patient with three days of clinical evolution before his hospitalization characterized by pain and phlogosis signs located in right iliac fossa, secondary to contusion in the region. It had a torpid evolution during the first days in hospital with soft tissue inflammation at the site of the bruising and pain associated with fever, chills, malaise, nausea, vomiting and diarrhea. The pain intensifies, the area of inflammation becomes to necrotic zone, finally the disease progresses to toxic shock and multiorganic failure.