Whole-plant and xylem hydraulics in poplar: insights gained from Populus deltoides - Populus nigra hybrids

We present results and insights gained from the characterization of the hydraulic architecture of eight field-grown Populus deltoides × Populus nigra genotypes, already known to differ in terms of growth performance, water-use and xylem anatomy (Marron et al. 2005, Monclus et al. 2005, 2006; Fichot et al. 2009). Under well-watered conditions, we provide evidence that (1) there are wide genotypic variations for hydraulic efficiency inferred from the leaf specific hydraulic conductance (kSL) and for resistance to drought-induced cavitation inferred from the water potential inducing 50% loss in hydraulic conductance, (2) a strong trade-off between water transport efficiency and xylem safety occurs at the whole plant level, indicating that genotypes with lower kSL apparently compensate the greater risks of embolism by building a safer xylem, (3) higher relative growth rate is tightly associated with lower whole-plant hydraulic efficiency and higher resistance to cavitation, (4) estimates of leaf water-use efficiency (intrinsic water use efficiency and carbon isotope discrimination against 13C) are weakly associated with whole-plant hydraulics. Under limited water supply, the characterization of xylem resistance to cavitation provides additional evidence that (5) xylem safety acclimates to moderate drought in a genotype-dependent manner, (6) there is no clear relationship between xylem safety and either xylem water transport efficiency or xylem biomechanics, contrary to what is observed at inter-specific scales. Our results provide interesting insights for the possible role of whole plant hydraulic architecture and xylem hydraulics in mediating key aspects of whole-plant physiology in poplar, such as growth and water-use efficiency. Finally, our results also indicate that there may be great opportunity for intra-specific comparisons to unravel specific issues that cannot be fully addressed by interspecific comparisons

Comparison of catheter-related infection risk in two different long-term venous devices in adult hematology-oncology patients Comparação do risco de infecção relacionada a cateteres entre dois tipos de dispositivos de longa permanência em pacientes onco-hematológicos

PURPOSE: Infection is the leading complication of long-term central venous catheters, and its incidence may vary according to catheter type. The objective of this study was to compare the frequency and probability of infection between two types of long-term intravenous devices. METHODS: Retrospective study in 96 onco-hematology patients with partially implanted catheters (n = 55) or completely implanted ones (n = 42). Demographic data and catheter care were similar in both groups. Infection incidence and infection-free survival were used for the comparison of the two devices. RESULTS: In a median follow-up time of 210 days, the catheter-related infection incidence was 0.2102/100 catheter-days for the partially implanted devices and 0.0045/100 catheter-days for the completely implanted devices; the infection incidence rate was 46.7 (CI 95% = 6.2 to 348.8). The 1-year first infection-free survival ratio was 45% versus 97%, and the 1-year removal due to infection-free survival ratio was 42% versus 97% for partially and totally implanted catheters, respectively (P <.001 for both comparisons). CONCLUSION: In the present study, the infection risk was lower in completely implanted devices than in partially implanted ones.<br>OBJETIVO: Infecção é a principal complicação relacionada ao uso de cateteres venosos de longa permanência em pacientes oncológicos e sua incidência pode variar a depender do tipo de cateter utilizado. O objetivo deste estudo foi comparar a freqüência e risco de infecção entre dois tipos de dispositivos de longa permanência. MÉTODOS: Estudo retrospectivo com 96 pacientes onco-hematológicos portadores de cateteres parcialmente implantáveis (n=55) ou totalmente implantáveis (n=42). Dados demográficos e cuidados com o dispositivo foram similares entre os dois grupos. A comparação entre os dispositivos foi realizada através da avaliação da incidência de infecção e da sobrevida livre de infecção. RESULTADOS: Em uma mediana de acompanhamento de 210 dias, a incidência de infecção relacionada ao cateter foi de 0,2102/100 cateter-dias para os dispositivos parcialmente implantáveis e de 0,0045/100 cateter-dias para os totalmente implantáveis, com uma razão de incidência de 46,7 (IC 95% = 6,2 a 348,8). A taxa de sobrevida livre de primeira infecção em um ano foi de 45% versus 97% e a taxa de sobrevida livre de retirada por infecção foi de 42% versus 97%, respectivamente para cateter parcialmente ou totalmente implantável (p<0,001 para ambas comparações). Conclusão: No presente estudo, o risco de infecção foi menor nos dispositivos totalmente implantáveis do que nos parcialmente implantáveis