123 research outputs found
Temporal, spatial, and structural patterns of adult trembling aspen and white spruce mortality in Quebec's boreal forest
Temporal, spatial, and structural patterns of adult trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) mortality were studied in intact 150-year-old stands in the southwestern boreal forest of Quebec. For both species, mortality decreases (number of dead trees/total number of trees) with distance from the lake edge until 100-150 m, from which point it slightly increases. Strong peaks in mortality were found for 40- to 60-year-old aspen mainly between 1974 and 1992. Such mortality in relatively young aspen is likely related to competition for light from the dominant canopy trees. Also, the recruitment of this young aspen cohort is presumably the result of a stand breakup that occurred when the initial aspen-dominated stand was between 90 and 110 years old. For spruce, strong peaks in mortality were found in 110- to 150-year-old trees and they occurred mainly after 1980. No clear explanation could be found for these peaks, but we suggest that they may be related to senescence or weakening of the trees following the last spruce budworm outbreak. Suppressed and codominant aspen had a much higher mortality ratio than spruce in the same height class, while more surprisingly, no difference in mortality rate was found between dominant trees of the two species. Most spruce trees were found as standing dead, which leads us to reject the hypothesis that windthrow is an important cause of mortality for spruce in our forests
RecombinantWolbachia surface protein (WSP)-induced T cell responses in Wuchereria bancrofti infections
Human lymphatic filariasis is a debilitating parasitic
disease characterized by downregulation of the hostâs
immune response in asymptomatic carriers along with
profound hyperreactivity in chronic patients apart from
putatively immune endemic normals. The endosymbiont
Wolbachia, a bacterium of filarial nematodes has received
much attention as possible chemotherapeutic target and its
involvement in disease pathogenesis. The role of recombinant
Wolbachia surface protein (rWSP), one of the most
abundantly expressed proteins of the endosymbiont, in
modulating cell-mediated immune responses in patients
harboring Wuchereria bancrofti infections was evaluated in
the current study. rWSP-induced lymphoproliferation with
peripheral blood mononuclear cells suggested an impaired
proliferative response in asymptomatic microfilaremic (MF)
and symptomatic chronic pathology (CP) patients compared
to endemic normals (EN). This was further supported by a significantly diminished expression of CD69 along with
elevated levels of CD127 and CD62L in filarial patients
(MF and CP) compared to EN. Further, rWSP induced
the expression of regulatory T cell markers CTLA-4 and
CD25 along with suppressor cytokines IL-10 and TGF-ÎČ
in MF and CP patients compared to EN. However, the
rWSP-stimulated expression of IFN-Îł was diminished
significantly in filarial patients compared to endemic
normals. Thus, these findings suggest that WSP may also
contribute to the suppression of immune responses seen
in filarial patients
Population dynamics of tropical forest trees
SIGLEAvailable from British Library Document Supply Centre- DSC:DX176568 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Sumber daya nabati Asia Tenggara no.6: :ROTAN/ N. Manokaran ; J. Dransfield (edt)
162 hal: ill ; 25 cm
Sumber daya nabati Asia Tenggara no.6: :ROTAN/ N. Manokaran ; J. Dransfield (edt)
162 hal: ill ; 25 cm
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