Minimum Variance Estimation of Yield Parameters of Rubber Tree with Kalman Filter

Although growth and yield data are available in rubber plantations in Nigeria for aggregate rubber production planning, existing models poorly estimate the yield per rubber tree for the incoming year. Kalman lter, a exible statistical estimator, is used to combine the inexact prediction of the rubber production with an equally inexact rubber yield, tree girth, tapping height, stimulation and tapping system measurements to obtain an optimal estimate of one year ahead rubber production. Six rubber clones-GT1, PB260, PB217, PB28/59, PB324 and RRIM703 were studied using 12-year data, generated from permanent experimental plots. Stochastic autoregressive model was tted to the data to identify optimal management strategy that accounts for risk due to seasonality. STAMP, an OxMetric modular software system for time series analysis, was used to estimate the yield parameters. Our results show that signi cant test of actual yield to model forecast is less than 1.96. Hence, the null hypothesis that the actual yield is within the forecasted value is accepted at 5% signi cant level. Based on the impulse response function of the lead equations, the long-run elasticity of yield was estimated to be highest for PB324 (2211gm/tree) and lowest for RRIM703 (1053gm/tree). PB260 is the best short term clone with the highest dynamic multiplier of 0.59. More important, the estimator minimized the variance of estimation errors from 55% of plantation prevision to 10%. It is our opinion that Kalman lter is a robust estimator of the biotechnical dynamics of rubber exploitation system.Keywords: Kalman lter, parameter estimation, rubber clones, Chow failure test, autocorrelation, STAMP, data characterizatio

Specific antibody levels and antigenic recognition of Wistar rats inoculated with distinct isolates of Trypanosoma evansi

"Mal de Cadeiras", an enzootic disease caused by Trypanosoma evansi, is one of the most important trypanosomiases in the Brazilian Pantanal region. The disease affects mainly horses, which are widely used in extensive cattle production, an activity of greatest economical significance for the region. The parasite also infects sylvan (coatis and capybaras) and domestic (dogs) animals, respectively considered wild and domestic reservoirs of T. evansi. For a better understanding of the interaction of T. evansi with its rodent host, we evaluated the differences in the specific antibody level patterns and in the parasitic peptides recognition patterns of experimentally infected Wistar rats. The rats experimentally infected with T. evansi isolates obtained from coatis, dogs and horses were submitted to indirect immunofluorescence test (IgM e IgG) and Western blotting. The serological titers for IgM and IgG ranged between 1:40 and 1:160. The most recognized polypeptide profiles were in a range of 17 and 74 kDa. Our data suggest that the humoral immune response in Wistar rats is not sufficient for granting an effective control of T. evansi infections

Trypanocidal activity of human plasma on Trypanosoma evansi in mice Atividade tripanocida do plasma humano sobre Trypanosoma evansi em camundongos

This study aimed to test an alternative protocol with human plasma to control Trypanosoma evansi infection in mice. Plasma from an apparently 27-year-old healthy male, blood type A+, was used in the study. A concentration of 100 mg.dL-1 apolipoprotein L1 (APOL1) was detected in the plasma. Forty mice were divided into four groups with 10 animals each. Group A comprised uninfected animals. Mice from groups B, C and D were inoculated with a T. evansi isolate. Group B was used as a positive control. At three days post-infection (DPI), the mice were administered intraperitoneally with human plasma. A single dose of 0.2 mL plasma was given to those in group C. The mice from group D were administered five doses of 0.2 mL plasma with a 24 hours interval between the doses. Group B showed high increasing parasitemia that led to their death within 5 DPI. Both treatments eliminated parasites from the blood and increased the longevity of animals. An efficacy of 50 (group C) and 80% (group D) of human plasma trypanocidal activity was found using PCR. This therapeutic success was likely achieved in the group D due to their higher levels of APOL1 compared with group C.<br>Este estudo teve como objetivo testar um protocolo alternativo com plasma humano para controlar a infecção por Trypanosoma evansi em camundongos. O plasma foi oriundo de um homem aparentemente saudável, com idade entre 27 anos e tipo de sangue A+. Foi detectada uma concentração de 100 mg.dL -1 de apolipoproteína L1 (APOL1) no plasma. Quarenta camundongos foram divididos em quatro grupos, contendo dez animais cada. Grupo A, composto de animais não infectados. Os roedores dos grupos B, C e D foram inoculados intraperitonealmente com um isolado de T. evansi. O Grupo B foi usado como um controle positivo. Três dias pós-infecção (DPI), os camundongos foram tratados com plasma humano. Uma dose única de 0,2 mL de plasma foi administrada nos roedores do grupo C. Os ratos do grupo D receberam cinco doses de 0,2 mL de plasma em intervalos de 24 horas. Os ratos do grupo B apresentaram parasitemia crescente, o que ocasionou a morte dos animais em 5 DPI. Ambos os tratamentos foram capazes de eliminar o parasito do sangue e aumentar a longevidade dos animais. O método da PCR detectou uma eficácia de 50% (grupo C) e 80% (grupo D) no tratamento com plasma humano. Este sucesso terapêutico obtido nos animais do grupo D provavelmente foi por receber maiores níveis de APOL1, comparado ao grupo C