Effect of the acclimation to high environmental temperature on the activity of hepatic glycogen phosphorylase (a+b and a), liver glycogen content and blood glucose level in rats

(1) Changes in the activity of hepatic glycogen phosphorylase a+b and a (GPh-ase a+b and a), liver glycogen content and blood glucose level during acclimation to moderate high environmental temperature (35±1 °C) were studied. (2) Experiments were carried out on adult fed Wistar rats of both sexes, previously given either short-term (1, 4 and 7 days) or long-term (14, 21, 30 and 60 days) exposure to high environmental temperature. The controls were continuously kept at room temperature (20±2 °C). (3) The results obtained showed that in the period of short-term exposure the liver glycogen content was decreased significantly (after the first and fourth days in male rats and after first day in female rats) and the GPh-ase a activity increased (after first day in male rats and after first, fourth and seventh day in female rats). Long-term exposure caused significant increased liver glycogen content (beginning from the 14th day in male rats and the 21st day in female rats) until the end of the acclimation period (60 days). The elevated activity of GPh-ase a persists after 14th day of exposure only in female rats while there are no significant changes over the rest of the acclimation period in both sexes. There were no significant changes in total GPh-ase activity during the whole period of exposure. Blood glucose level was significantly decreased throughout the whole period of acclimation to high environmental temperature, in both sexes (except in the 1 day exposed groups). (4) The increased activity of hepatic GPh-ase a and decreased glycogen content suggested that the short-term exposure to heat stimulates the glycogenolytical processes. Decreased blood glucose level, and elevated liver glycogen content (r=-0.7467 in male and r=-0.6548 in female rats) suggested that prolonged exposure to high environmental temperature stimulated glycogenogenesis, without changes in the GPh-ase activity.     

Conformational changes of beta-lactoglobulin in sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles. A fluorescence and CD study.

The effect of beta-lactoglobulin encapsulation in sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles on the environment of protein and on Trp was analysed at different water contents (omega0). CD data underlined the distortion of the beta-sheet and a less constrained tertiary structure as the omega0 increased, in agreement with a concomitant red shift and a decrease in the signal intensity obtained in steady-state fluorescence measurements. Fluorescence lifetimes, evaluated by biexponential analysis, were tau1 = 1.28 ns and tau2 = 3.36 ns in neutral water. In reverse micelles, decay-associated spectra indicated the occurrence of important environmental changes associated with omega0. Bimolecular fluorescence quenching by CCl4 and acrylamide was employed to analyse alterations in the accessibility of the two Trp residues in beta-lactoglobulin, induced by changes in omega0. The average bimolecular quenching constant was found not to depend on omega0, confirming the insolubility of this quencher in the aqueous interface, while increases with omega0. The drastic decrease with omega0 of kq, associated with the longest lifetime kq2(CCl4), comparatively to the increase of kq2(acrylamide), emphasizes the location of beta-lactoglobulin in the aqueous interfacial region especially at omega0> or = 10. The fact that (omega0 = 30) > kq2(acrylamide) (water) also confirms the important conformational changes of encapsulated beta-lactoglobulin.     

Synthetic prions with novel strain-specified properties

Prions are infectious proteins that possess multiple self-propagating structures. The information for strains and structural specific barriers appears to be contained exclusively in the folding of the pathological isoform, PrP^Sc. Many recent studies determined that de novo prion strains could be generated in vitro from the structural conversion of recombinant (rec) prion protein (PrP) into amyloidal structures. Our aim was to elucidate the conformational diversity of pathological recPrP amyloids and their biological activities, as well as to gain novel insights in characterizing molecular events involved in mammalian prion conversion and propagation. To this end we generated infectious materials that possess different conformational structures. Our methodology for the prion conversion of recPrP required only purified rec full-length mouse (Mo) PrP and common chemicals. Neither infected brain extracts nor amplified PrP^Sc were used. Following two different in vitro protocols recMoPrP converted to amyloid fibrils without any seeding factor. Mouse hypothalamic GT1 and neuroblastoma N2a cell lines were infected with these amyloid preparations as fast screening methodology to characterize the infectious materials. Remarkably, a large number of amyloid preparations were able to induce the conformational change of endogenous PrP^C to harbor several distinctive proteinase-resistant PrP forms. One such preparation was characterized in vivo habouring a synthetic prion with novel strain specified neuropathological and biochemical properties.     

Intraspecific variation in Gracilaria caudata (Gracilariales,Rhodophyta): growth,pigment content,and photosynthesis

In Brazil, one of the probable reasons for failure in attempts at macroalgal mariculture is the lack of previous studies under controlled conditions. Gracilaria caudata is an important marine red alga which is locally exploited for the production of agar. In this study the aim was to compare in vitro growth rates, pigment content, and photosynthesis in gametophytes and tetrasporophytes of G. caudata from two distinct geographical areas located 2,500 km apart on the Brazilian coast, one in a warmer area closer to the equator (northeastern population), and the other in a colder area closer to the Tropic of Capricorn (southeastern population). Additionally, the artificial ultraviolet B (UVB) radiation effects on strains were evaluated. Under UVB, deleterious effects were observed in all strains. Although the strains from the southeastern population had higher growth rates than those from the northeastern under control condition, the opposite was observed under UVB condition. Under controlled conditions and regardless of the population, growth rates, net photosynthesis, P _max, I _k, and pigment contents were higher in tetrasporophytes than in gametophytes. Consequently, when determining the real potential of a certain phase in cultivation, the tetrasporophyte appears to be the more promising for future experiments along the Brazilian coast. Furthermore, although the growth rate of southeastern strains under control condition was higher, their higher sensitivity to UVB radiation emphasizes the importance of careful selection of the most suitable sites prior to experimental cultivation. The differences in performance between the southeastern and northeastern strains provide support for the hypothesis of their ecotypic differentiation.     

Intralesional uridine-5′-triphosphate (UTP) treatment induced resistance to <Emphasis Type="Italic">Leishmania amazonensis</Emphasis> infection by boosting Th<Subscript>1</Subscript> immune responses and reactive oxygen species production

Leishmania amazonensis is the etiologic agent of cutaneous leishmaniasis, an immune-driven disease causing a range of clinical symptoms. Infections caused by L. amazonensis suppress the activation and function of immune cells, including macrophages, dendritic cells, and CD4⁺ T cells. In this study, we analyzed the course of infection as well as the leishmanicidal effect of intralesional UTP treatment in L. amazonensis-infected BALB/c mice. We found that UTP treatment reduced the parasitic load in both footpad and lymph node sites of infection. UTP also boosted Th1 immune responses, increasing CD4⁺ T cell recruitment and production of IFN-γ, IL-1β, IL-12, and TNF-α. In addition, the role of UTP during innate immune response against L. amazonensis was evaluated using the air pouch model. We observed that UTP augmented neutrophil chemoattraction and activated microbicidal mechanisms, including ROS production. In conclusion, our data suggested an important role for this physiological nucleotide in controlling L. amazonensis infection, and its possible use as a therapeutic agent for shifting immune responses to Th1 and increasing host resistance against L. amazonensis infection.     

Improved Sprouting and Growth of Mung Plants in Chromate Contaminated Soils Treated with Marine Strains of <Emphasis Type="Italic">Staphylococcus</Emphasis> Species

Marine bacteria possess a wide variety of bioremediation potential which is beneficial environmentally and economically. In this study, bacterial isolates from marine waters were screened for tolerance and growth in high concentrations of chromate (Cr⁶⁺). Two isolates, capable of tolerating Cr⁶⁺ concentrations 300 µg mL^?1 or higher, and found to completely reduce 20 µg mL^?1 Cr⁶⁺ were grown in Cr⁶⁺ (50 and 100 mg kg^?1) spiked garden soil. Notably, both facilitated normal germination and growth of mung (Vigna radiata) seeds, which could hardly germinate in Cr⁶⁺ spiked garden soil without either of these bacteria. In fact, large percent of mung seeds failed to sprout in the Cr⁶⁺ spiked garden soil and could not grow any further. Apparently, chromate detoxification by marine bacterial isolates and the ability of mung plants to deal with the reduced form appear to work complementarily. This study provides an insight into marine bacterial abilities with respect to chromium and potential applications in promoting growth of leguminous plants-similar to mung in particular-in Cr⁶⁺ contaminated soil.     

Chk2 suppresses the oncogenic potential of DNA replication-associated DNA damage

The Mre11 complex (Mre11, Rad50, and Nbs1) and Chk2 have been implicated in the DNA-damage response, an inducible process required for the suppression of malignancy. The Mre11 complex is predominantly required for repair and checkpoint activation in S phase, whereas Chk2 governs apoptosis. We examined the relationship between the Mre11 complex and Chk2 in the DNA-damage response via the establishment of Nbs1(DeltaB/DeltaB) Chk2(-/-) and Mre11(ATLD1/ATLD1) Chk2(-/-) mice. Chk2 deficiency did not modify the checkpoint defects or chromosomal instability of Mre11 complex mutants; however, the double-mutant mice exhibited synergistic defects in DNA-damage-induced p53 regulation and apoptosis. Nbs1(DeltaB/DeltaB) Chk2(-/-) and Mre11(ATLD1/ATLD1) Chk2(-/-) mice were also predisposed to tumors. In contrast, DNA-PKcs-deficient mice, in which G1-specific chromosome breaks are present, did not exhibit synergy with Chk2(-/-) mutants. These data suggest that Chk2 suppresses the oncogenic potential of DNA damage arising during S and G2 phases of the cell cycle.     

Brucella control of dendritic cell maturation is dependent on the TIR-containing protein Btp1

Brucella is an intracellular pathogen able to persist for long periods of time within the host and establish a chronic disease. We show that soon after Brucella inoculation in intestinal loops, dendritic cells from ileal Peyer's patches become infected and constitute a cell target for this pathogen. In vitro, we found that Brucella replicates within dendritic cells and hinders their functional activation. In addition, we identified a new Brucella protein Btp1, which down-modulates maturation of infected dendritic cells by interfering with the TLR2 signaling pathway. These results show that intracellular Brucella is able to control dendritic cell function, which may have important consequences in the development of chronic brucellosis.     

The mitochondrial kinase PINK1, stress response and Parkinson’s disease

Mitochondrial dysfunction is well documented in presymptomatic brain tissue with Parkinson’s disease (PD). Identification of the autosomal recessive variant PARK6 caused by loss-of-function mutations in the mitochondrial kinase PINK1 provides an opportunity to dissect pathogenesis. Although PARK6 shows clinical differences to PD, the induction of alpha-synuclein “Lewy” pathology by PINK1-deficiency proves that mitochondrial pathomechanisms are relevant for old-age PD. Mitochondrial dysfunction is induced by PINK1 deficiency even in peripheral tissues unaffected by disease, consistent with the ubiquitous expression of PINK1. It remains unclear whether this dysfunction is due to PINK1-mediated phosphorylation of proteins inside or outside mitochondria. Although PINK1 deficiency affects the mitochondrial fission/fusion balance, cell stress is required in mammals to alter mitochondrial dynamics and provoke apoptosis. Clearance of damaged mitochondria depends on pathways including PINK1 and Parkin and is critical for postmitotic neurons with high energy demand and cumulative stress, providing a mechanistic concept for the tissue specificity of disease.