Sexual hormones: effects on cardiac and mitochondrial activity after ischemia-reperfusion in adult rats. Gender difference

In this work we studied the influence of sex hormones on heart and mitochondrial functions, from adult castrated female and male, and intact rats. Castration was performed at their third week of life and on the fourth month animals were subjected to heart ischemia and reperfusion. Electrocardiogram and blood pressure recordings were made, cytokines levels were measured, histopathological studies were performed and thiobarbituric acid reactive species were determined. At the mitochondrial level respiratory control, transmembranal potential and calcium management were determined; Western blot of some mitochondrial components was also performed. Alterations in cardiac function were worst in intact males and castrated females as compared with those found in intact females and castrated males, cytokine levels were modulated also by hormonal status. Regarding mitochondria, in those obtained from hearts from castrated females without ischemia-reperfusion, all evaluated parameters were similar to those observed in mitochondria after ischemia-reperfusion. The results show hormonal influences on the heart at functional and mitochondrial levels.     

CCS52 and DEL1 genes are key components of the endocycle in nematode‐induced feeding sites

The establishment of galls and syncytia as feeding sites induced by root‐knot and cyst nematodes, respectively, involves a progressive increase in nuclear and cellular size. Here we describe the functional characterization of endocycle activators CCS52A, CCS52B and a repressor of the endocycle, DEL1, during two types of nematode feeding site development in Arabidopsis thaliana. In situ hybridization analysis showed that expression of CCS52A1 and CCS52B was strongly induced in galls and syncytia and DEL1 was stably but weakly expressed throughout feeding site development. Down‐regulation and over‐expression of CCS52 and DEL1 in Arabidopsis drastically affected giant cell and syncytium growth, resulting in restrained nematode development, illustrating the need for mitotic activity and endo‐reduplication for feeding site maturation. Exploiting the mechanism of endo‐reduplication may be envisaged as a strategy to control plant‐parasitic nematodes.     

Biochemical characterization and comparative analysis of two distinct serine proteases from Bothrops pirajai snake venom

This study reports the isolation and biochemical characterization of two different serine proteases from Bothrops pirajai snake venom, thus providing a comparative analysis of the enzymes. The isolation process consisted of three consecutive chromatographic steps (Sephacryl S-200, Benzamidine Sepharose and C2/C18), resulting in two serine proteases, named BpirSP27 and BpirSP41 after their molecular masses by mass spectrometry (27,121 and 40,639 Da, respectively). Estimation by SDS-PAGE under denaturing conditions showed that, when deglycosylated with PNGase F, BpirSP27 and BpirSP41 had their molecular masses reduced by approximately 15 and 42%, respectively. Both are acidic enzymes, with pI of approximately 4.7 for BpirSP27 and 3.7 for BpirSP41, and their N-terminal amino acid sequences showed 57% identity to each other, with high similarity to the sequences of other snake venom serine proteases (SVSPs). The enzymes showed different actions on bovine fibrinogen, with BpirSP27 acting preferentially on the Bβ chain and BpirSP41 on both Aα and Bβ chains. The two serine proteases were also able to degrade fibrin and blood clots in vitro depending on the doses and incubation periods, with higher results for BpirSP41. Both enzymes coagulated the human plasma in a dose-dependent manner, and BpirSP41 showed a higher coagulant potential, with minimum coagulant dose (MCD) of ∼3.5 μg versus 20 μg for BpirSP27. The enzymes were capable of hydrolyzing different chromogenic substrates, including S-2238 for thrombin-like enzymes, but only BpirSP27 acted on the substrate S-2251 for plasmin. They also showed high stability against variations of temperature and pH, but their activities were significantly reduced after preincubation with Cu²⁺ ion and specific serine protease inhibitors. In addition, BpirSP27 induced aggregation of washed platelets to a greater extent than BpirSP41. The results showed significant structural and functional differences between B. pirajai serine proteases, providing interesting insights into the structure–function relationship of SVSPs.     

Trypanosoma cruzi: in vivo evaluation of iron in skin employing X-ray fluorescence (XRF) in mouse strains that differ in their susceptibility to infection

Trypanosoma cruzi, the causative agent of Chagas' disease (CD), is a substantial public health concern in Latin America. Laboratory mice inoculated with T. cruzi have served as important animal models of acute CD. Host hypoferremic responses occur during T. cruzi infection; therefore, it has been hypothesized that T. cruzi requires iron for optimal growth in host cells and, unlike extracellular pathogens, may benefit from host hypoferremic responses. Recent technological improvements of X-ray fluorescence are useful for diagnostics or monitoring in biomedical applications. The goal of our study was to determine whether the iron availabilities in Swiss and C57BL/6 mice differ during the acute phase of T. cruzi infection and whether the availability correlates with oxidative stress in the susceptible and resistant phenotypes identified in these mice. Our results showed that the decrease in iron levels in the skin of resistant infected mice correlated with the increase in oxidative stress associated with anemia and the reduction in parasite burden.     

Phenotypic flexibility in basal metabolic rate is associated with rainfall variability among populations of rufous-collared sparrow

Phenotypic flexibility in metabolic rates allows organisms to reversibly adjust their energy flow to meet challenges imposed by a variable environment. In turn, the food habits hypothesis (FHH) predicts that species or populations adjust their basal metabolic rate (BMR) according to the diet attributes such as food abundance or predictability. Desert ecosystems represent a temporally heterogeneous environment because of low rain pulse predictability, which is also associated with temporal variation in food resources. In the present study, we investigated the relationship between the magnitude of BMR flexibility in response to dietary acclimation and the inter-annual rainfall variability in three populations of rufous-collared sparrows. Specifically we addressed the question of whether birds from a desert environment are more flexible in BMR than those from non-desert habitats. We found a positive trend between BMR flexibility and the inter-annual rainfall variability. In fact, dietary treatments had a significant effect only in desert birds, a result that also supported the FHH. Our study confirms the existence of phenotypic variation in response to environmental conditions among populations, and also highlights the importance of considering the circumstances in which phenotypic flexibility evolves and the specific environmental cues that induce their expression.     

Daily Temperature Amplitude Affects the Vegetative Growth and Carbon Metabolism of Orange Trees in a Rootstock-Dependent Manner

Both instantaneous and average growth temperatures affect plant metabolism, and the physiological importance of daily variations in temperature is frequently underestimated. To improve our understanding of the environmental regulation of citrus trees, we hypothesized that vegetative growth would be stimulated in orange plants subjected to large daily temperature variations, even without changes in the average daily air temperature or the amount of energy given by degree-days. This hypothesis was tested with orange plants grafted onto Rangpur lime or Swingle citrumelo rootstocks and grown for 20?days under thermal regimes (day/night) of 25/25°C or 32.5/17.5°C. Such regimes imposed growth conditions with daily temperature variations of 0 and 15°C. Plant growth, photosynthesis, respiration, and carbohydrate availability in leaves, stems, and roots were measured under both thermal conditions. The daily temperature variation affected the carbon metabolism of young citrus trees; plants grown under daily variation of 15°C used more of the carbon stored in mature leaves and roots and the energy generated by respiration for the biosynthesis of vegetative structures, such as leaves and branches. Thus, there was a significant increase in the leaf area of plants subjected to high daily temperature variation. Current photosynthesis was similar in the two thermal regimes; however, the photosynthetic rates increased under the 15°C variation when measurements were normalized to 25°C. In addition to the stimulatory effect of the source?Csink relationship on photosynthesis, we suggest a probable involvement of hormonal regulation of plant growth through gibberellin metabolism. The rootstock affected the response of the canopy to daily temperature amplitude, with the Rangpur lime improving plant growth through higher carbohydrate availability in roots. This is the first report that highlights the importance of daily temperature variations for citrus growth and physiology under nonlimiting conditions.