Heat shock proteins (HSPs) are abundantly produced in cells that are under stress or injury by acting as a chaperone or promoting folding, unfolding, packing, degradation or denaturing of proteins or peptides. This study evaluated the role of HSP60, HSP70 or HSP90 in the rostral ventrolateral medulla (RVLM), in experimental endotoxemia in the rat. Adult, male Sprague-Dawley rats maintained by i.v. infusion propofol (25 mg/kg/h) were used. During experimental endotoxemia induced by intravenous administration of E. coli lipopolysaccharide (LPS, 30 mg/kg; serotype 0111:B4), the power density of the vasomotor component of systemic arterial pressure (SAP) spectrum underwent a decrease (Phase I), followed by an increase (Phase II; ¡§pro-life¡¨) and a secondary decrease (Phase III; ¡§pro-death¡¨). Western blot analysis revealed that HSP60 expression in the RVLM was significantly increased during Phase II and Phase III endotoxemia; and HSP70 expression was maximally increased during Phase II. HSP90 protein expression in the RVLM was not significantly changed during endotoxemia. We further studied the role of HSP60, HSP70 or HSP90 at the RVLM in experimental endotoxemia by pretreating animals with bilaterally microinjection of an anti-HSP serum (HSPAb, 1:20), normal mouse serum, antisense oligodeoxynucleotide (hsp AODN, 50 pmol), sense oligodeoxynucleotide (hsp SODN) or scrambled AODN (hsp SC). Pretreatment with HSP60Ab or hsp60 AODN resulted in significantly higher mortality, shorter survival time and shorter Phase II duration. In addition, the augmented power density of the vasomotor component of SAP signals during Phase II endotoxemia was significantly reduced. Even more detrimental effects were obtained on local application of HSP70Ab or hsp70 AODN into the RVLM. Pretreatment with HSP90Ab or hsp90 AODN was ineffective. We conclude that the expression of HSP60 and HSP70 in the RVLM may play a ¡§pro-life¡¨ role in fatal experimental endotoxemia; and HSP90 may not be involved.

Studies of seed dynamics and seedling establishment at the community level in savanna ecosystems are scant, particularly in the tropical savannas of Central Brazil. The Brazilian savannas (cerrado) have the largest diversity of plant species among Neotropical savannas. Cerrado vegetation exhibits consistent changes in tree density and tree size along shallow topographic gradients. Vegetation types differ from closed savannas with high tree density, and a nearly continuous canopy cover in the uppermost portions, to open savannas with scattered short trees in the low portions of the topographic gradients. Whether or not dynamics of seeds and seedlings of woody species are consistent with variations in tree density and tree canopy cover across the cerrado landscape has not been determined, but could potentially influence such spatial patterns of tree density and canopy cover. The main objective of this study was to evaluate seed dynamics (i.e., seed rain, soil seed banks, and seed characteristics) and seedling establishment of woody species in three major cerrado vegetation types (closed, intermediate and open savannas) which differ in tree canopy cover and tree height. These vegetation types are located along topographic gradients of approximately 30 m in elevation and 1000 m in length. I conducted field work from June 2005 to August 2008 at the Instituto Brasileiro de Geografia e Estatística (IBGE) reserve, a field experimental station located 35 Km south of Brasilia, Brazil (15˚ 56' S, 47˚ 63' W, altitude 1100 m). I established permanent plots in each of the three vegetation types to assess seed rain, seed limitation, seed predation, and seed removal. I also quantified density and composition of the soil seed bank in each vegetation type and studied seed characteristics (i.e., kind of dormancy, moisture content, longevity) of 14 common cerrado woody species. In the field, I quantified establishment of woody seedlings in fire-protected savannas as well as in accidentally burned and frequently burned savannas. In the greenhouse I performed experiments to evaluate the effect of litter cover and light level on seedling emergence of 9 common cerrado woody species. Finally, I evaluated the effect of pulses of heat on seed germination of 5 common cerrado woody species under controlled conditions. The overall results of this study show that regardless of tree canopy cover, cerrado vegetation types are limited in seeds and seedlings of woody species, but these limitations are higher in open than in closed savannas. Most woody species do not form persistent soil seed banks along cerrado vegetation types because their seeds are short-lived, predated and quickly removed from the ground. In addition, dispersal season and dormancy appear to control timing of germination at the onset of the rainy season to ensure survival of seedlings in the field. In the absence of fire, establishment of woody seedlings is higher in closed than in open savannas because canopy cover mitigates the stressful environmental conditions of open savannas and thus facilitates establishment of woody seedlings. As a result, closed savannas are likely to maintain higher density of woody elements over time than open savannas. In burned savannas, however, species composition of woody and herbaceous seedlings is significantly affected because establishment of seedlings of woody and herbaceous species decreases but vegetative reproduction increases. This dissertation study indicates that interactions of early life-history stages of woody species with environmental and disturbance factors appear to play a more significant role in maintaining woody cover variations along cerrado topographic gradients than previously recognized.