Cardiac glycogen accumulation after dexamethasone is regulated by AMPK

Glycogen is an immediate source of glucose for cardiac tissue to maintain its metabolic homeostasis. However, its excess brings about cardiac structural and physiological impairments. Previously, we have demonstrated that in hearts from dexamethasone (Dex)-treated animals, glycogen accumulation was enhanced. We examined the influence of 5'-AMP-activated protein kinase (AMPK) on glucose entry and glycogen synthase as a means of regulating the accumulation of this stored polysaccharide. After Dex, cardiac tissue had a limited contribution toward the development of whole body insulin resistance. Measurement of glucose transporter 4 (GLUT4) at the plasma membrane revealed an excess presence of this transporter protein at this location. Interestingly, this was accompanied by an increase in GLUT4 in the intracellular membrane fraction, an effect that was well correlated with increased GLUT4 mRNA. Both total and phosphorylated AMPK increased after Dex. Immunoprecipitation of Akt substrate of 160 kDa (AS160) followed by Western blot analysis demonstrated no change in Akt phosphorylation at Ser(473) and Thr(308) in Dex-treated hearts. However, there was a significant increase in AMPK phosphorylation at Thr(172), which correlated well with AS160 phosphorylation. In Dex-treated hearts, there was a considerable reduction in the phosphorylation of glycogen synthase, whereas glycogen synthase kinase-3-beta phosphorylation was augmented. Our data suggest that AMPK-mediated glucose entry combined with the activation of glycogen synthase and a reduction in glucose oxidation (Qi et al., Diabetes 53: 1790-1797, 2004) act together to promote glycogen storage. Should these effects persist chronically in the heart, they may explain the increased morbidity and mortality observed with long-term excesses in endogenous or exogenous glucocorticoids.     

Transformations of chloroguaiacols, chloroveratroles, and chlorocatechols by stable consortia of anaerobic bacteria

Metabolically stable consortia of anaerobic bacteria obtained by enrichment of sediment samples with 3,4,5-trimethoxybenzoate (TMBA), 3,4,5-trihydroxybenzoate (gallate [GA]), or 5-chlorovanillin (CV) were used to study the anaerobic transformation of a series of chloroveratroles, chloroguaiacols, and chlorocatechols used as cosubstrates. Experiments were carried out with growing cultures, and the following pathways were demonstrated for metabolism of the growth substrates: (i) TMBA produced GA, which was further degraded without the formation of aromatic intermediates; (ii) GA formed pyrogallol, which was stable to further transformation; and (iii) CV was degraded by a series of steps involving de-O-methylation, oxidation of the aldehyde group, and decarboxylation to 3-chlorocatechol before ring cleavage. Mono-de-O-methylation of the cosubstrates occurred rapidly in the order 4,5,6-trichloroguaiacol greater than 3,4,5-trichloroguaiacol approximately 3,4,5-trichloroveratrole approximately tetrachloroveratrole greater than tetrachloroguaiacol and was concomitant with degradation of the growth substrates. For the polymethoxy compounds--chloroveratroles, 1,2,3-trichloro-4,5,6-trimethoxybenzene, and 4,5,6-trichlorosyringol--de-O-methylation took place sequentially. The resulting chlorocatechols were stable to further transformation until the cultures had exhausted the growth substrates; selective dechlorination then occurred with the formation of 3,5-dichlorocatechol from 3,4,5-trichlorocatechol and of 3,4,6-trichlorocatechol from tetrachlorocatechol. 2,4,5-, 2,4,6-, and 3,4,5-trichoroanisole and 2,3,4,5-tetrachloroanisole were de-O-methylated, but the resulting chlorophenols were resistant to dechlorination. These results extend those of a previous study with spiked sediment samples and their endogenous microflora and illustrate some of the transformations of chloroguaiacols and chlorocatechols which may be expected to occur in anaerobic sediments.     

Muscular Weakness in Individuals with HIV Associated with a Disorganization of the Cortico-Spinal Tract: A Multi-Modal MRI Investigation

Motor impairment is highly prevalent in HIV-infected patients. Here, we assess associations between peripheral muscular deficits as evaluated by the 5 sit-to-stand test (5STS) and structural integrity of the motor system at a central level. Eighty-six HIV-infected patients receiving combination antiretroviral therapy and with no major cerebral events, underwent an MRI scan and the 5STS. Out of 86 participants, forty presented a score greater than two standard deviations above mean normative scores calculated for the 5STS and were therefore considered as motor-impaired. MRI-structural cerebral parameters were compared to the unimpaired participants. Fractional Anisotropy (FA), Axial Diffusivity (AD) and Radial Diffusivity (RD), reflecting microstructural integrity, were extracted from Diffusion-Tensor MRI. Global and regional cerebral volumes or thicknesses were extracted from 3D-T1 morphological MRI. Whereas the two groups did not differ for any HIV variables, voxel-wise analysis revealed that motor-impaired participants present low FA values in various cortico-motor tracts and low AD in left cortico-spinal tract. However, they did not present reduced volumes or thicknesses of the precentral cortices compared to unimpaired participants. The absence of alterations in cortical regions holding motor-neurons might argue against neurodegenerative process as an explanation of White Matter (WM) disorganization.     

Multiple Feedbacks Contribute to a Centennial Legacy of Reindeer on Tundra Vegetation

Historical contingency is the impact of past events, like the timing and order of species arrival, on community assembly, and can sometimes result in alternative stable states of ecological communities. Large herbivores, wild and domestic, can cause profound changes in the structure and functioning of plant communities and therefore probably influence historical contingency; however, little empirical data on the stability of such shifts or subsequent drivers of stability are available. We studied the centennial legacy of reindeer (Rangifer tarandus) pressure on arctic tundra vegetation by considering historical milking grounds (HMGs): graminoid- and forb-dominated patches amid shrub-dominated tundra, formed by historical Sami reindeer herding practices that ended approximately 100 years ago. Our results show that the core areas of all studied HMGs remained strikingly stable, being hardly invaded by surrounding shrubs. Soil nitrogen concentrations were comparable to heavily grazed areas. However, the HMGs are slowly being reinvaded by vegetative growth of shrubs at the edges, and the rate of ingrowth increased with higher mineral N availability. Furthermore, our data indicate that several biotic feedbacks contribute to the stability of the HMGs: increased nutrient turnover supporting herbaceous vegetation, strong interspecific competition preventing invasion and herbivore damage to invading shrubs. In particular, voles and lemmings appear to be important, selectively damaging shrubs in the HMGs. We concluded that HMGs provide clear evidence for historical contingency of herbivore effects in arctic ecosystems. We showed that several biotic feedbacks can contribute to subsequent vegetation stability, but their relative importance will vary in time and space.     

What Is the Future for Zoos and Aquariums?

ABSTRACT

Animal welfare concerns have plagued the professional zoo and aquarium field for decades. Societal differences remain concerning the well-being of animals, but it appears a shift is emerging. Scientific studies of animal welfare have dramatically increased, establishing that many previous concerns were not misguided public empathy or anthropomorphism. As a result, both zoo and aquarium animal welfare policy and science are now at the center of attention within the world’s professional zoos and aquariums. It is now possible to view a future that embraces the well-being of individual captive exotic animals, as well as that of their species, and one in which professional zoos and aquariums are dedicated equally to advancing both. Though the ethics of keeping exotic animals and animals from the wild in captivity are still a contentious subject both outside and even within the profession, this study argues. We argue that this path forward will substantially improve most zoo and aquarium animals' welfare and could significantly reduce societal concerns. If animal welfare science and policy are strongly rooted in compassion and embedded in robust accreditation systems, the basic zoo/aquarium paradigm will move toward a more thoughtful approach to the interface between visitors and animals. It starts with a fundamental commitment to the welfare of individual animals.     

Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae)

Individual plants of several Amelanchier taxa contain many polymorphic nucleotide sites in the internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA). This polymorphism is unusual because it is not recent in origin and thus has resisted homogenization by concerted evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the result of gene flow between two major North American clades resolved by phylogenetic analysis of ITS sequences. Western North American species plus A. humilis and A. sanguinea of eastern North America form one clade (A), and the remaining eastern North American Amelanchier make up clade B. Five eastern North American taxa are polymorphic at many of the nucleotide sites where clades A and B have diverged and are thought to be of hybrid origin, with A. humilis or A. sanguinea as one parent and various members of clade B as the other parent. Morphological evidence suggests that A. humilis is one of the parents of one of the polymorphic taxa, a microspecies that we refer to informally as A. "erecta." Sequences of 21 cloned copies of the ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical to A. humilis sequence or to the clade B consensus sequence, or they are apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier "erecta" and another polymorphic taxon are suspected to be relatively old because both grow several hundred kilometers beyond the range of one of their parents. ITS sequence polymorphisms have apparently persisted in these two taxa perhaps because of polyploidy and/or agamospermy (asexual seed production), which are prevalent in the genus.      

Intracellular Distribution of 5' Nucleotidase in Rat Liver

The intracellular distribution of 5' nucleotidase was investigated in rat liver by biochemical analysis of cell fractions obtained by differential centrifugation. The enzymatic activity was measured by determination of the inorganic phosphorus liberated from 5' nucleotides. The 5' nucleotidase activity was mainly found in the nuclear and microsomal fractions. An attempt to extract the enzyme from these fractions with Mg⁺⁺ ion solutions was unsuccessful. It is concluded that 5' nucleotidase is actually present in the nuclear and microsomal fractions of rat liver cells.