Tillering dynamics in palisadegrass swards continuously stocked by cattle

Plant communities on pastures adapt to varying frequencies and severities of defoliation through mechanisms capable of ensuring their longevity and photosynthetic efficiency. The objective of this experiment was to evaluate tiller population density, demographic patterns of tillering and population stability of palisadegrass swards subjected to four grazing intensities. Treatments corresponded to four sward steady state conditions (sward heights of 10, 20, 30 and 40 cm) generated by continuous stocking. Measurements of tiller population density and population dynamics were performed at 4 week intervals and the results were used to calculate tiller appearance, death and survival rates. Tiller appearance and death rate were used to calculate sward stability index. The results indicate that keeping swards low (10 cm or lower) may be prejudicial to persistency and productivity of palisadegrass. The results also indicate that a low tiller population alone should not be considered as an indicator of loss of productive potential and of reduced plant persistency, since swards may be stable even with low population of tillers.

Evaluating the efficiency of fractional integration parameter estimators

This article deals with the efficiency of fractional integration parameter estimators. This study was based on Monte Carlo experiments involving simulated stochastic processes with integration orders in the range]-1,1[. The evaluated estimation methods were classified into two groups: heuristics and semiparametric/maximum likelihood (ML). The study revealed that the comparative efficiency of the estimators, measured by the lesser mean squared error, depends on the stationary/non-stationary and persistency/anti-persistency conditions of the series. The ML estimator was shown to be superior for stationary persistent processes; the wavelet spectrum-based estimators were better for non-stationary mean reversible and invertible anti-persistent processes; the weighted periodogram-based estimator was shown to be superior for non-invertible anti-persistent processes.

Liver HLA-G expression is associated with multiple clinical and histopathological forms of chronic hepatitis B virus infection

As the mechanisms leading to the persistence of hepatitis B virus (HBV) infection are poorly understood and as the histocompatibility leucocyte antigen (HLA)-G is well described as a tolerogenic molecule, we evaluated HLA-G expression in 74 specimens of HBV liver biopsies and in 10 specimens obtained from previously healthy cadaver liver donors. HBV specimens were reviewed and classified by the METAVIR score, and HLA-G expression was assessed by immunohistochemistry. No HLA-G expression was observed in control hepatocytes. In contrast, 57 (77%) of 74 HBV specimens showed soluble and membrane-bound HLA-G expression in hepatocytes, biliary epithelial cells or both. No associations between the intensity of HLA-G expression and patient age or gender, HBeAg status, severity of liver fibrosis, and grade of histological findings were observed. Although significance was not reached (P = 0.180), patients exhibiting HLA-G expression presented a higher median HBV DNA viral load (105 copies/mL) than those who did not express HLA-G (103.7 copies/mL). These results indicate that HLA-G is expressed in most cases of chronic HBV infection in all stages and may play a role in the persistency of HBV infection.