Moonlighting kinases with guanylate cyclase activity can tune regulatory signal networks

Guanylate cyclase (GC) catalyzes the formation of cGMP and it is only recently that such enzymes have been characterized in plants. One family of plant GCs contains the GC catalytic center encapsulated within the intracellular kinase domain of leucine rich repeat receptor like kinases such as the phytosulfokine and brassinosteroid receptors. In vitro studies show that both the kinase and GC domain have catalytic activity indicating that these kinase-GCs are examples of moonlighting proteins with dual catalytic function. The natural ligands for both receptors increase intracellular cGMP levels in isolated mesophyll protoplast assays suggesting that the GC activity is functionally relevant. cGMP production may have an autoregulatory role on receptor kinase activity and/or contribute to downstream cell expansion responses. We postulate that the receptors are members of a novel class of receptor kinases that contain functional moonlighting GC domains essential for complex signaling roles.     

Stems cells and the pathways to aging and cancer

The aging of tissue-specific stem cell and progenitor cell compartments is believed to be central to the decline of tissue and organ integrity and function in the elderly. Here, we examine evidence linking stem cell dysfunction to the pathophysiological conditions accompanying aging, focusing on the mechanisms underlying stem cell decline and their contribution to disease pathogenesis.     

Identification of the endostyle as a stem cell niche in a colonial chordate

Stem cell populations exist in "niches" that hold them and regulate their fate decisions. Identification and characterization of these niches is essential for understanding stem cell maintenance and tissue regeneration. Here we report on the identification of a novel stem cell niche in Botryllus schlosseri, a colonial urochordate with high stem cell-mediated developmental activities. Using in vivo cell labeling, engraftment, confocal microscopy, and time-lapse imaging, we have identified cells with stemness capabilities in the anterior ventral region of the Botryllus' endostyle. These cells proliferate and migrate to regenerating organs in developing buds and buds of chimeric partners but do not contribute to the germ line. When cells are transplanted from the endostyle region, they contribute to tissue development and induce long-term chimerism in allogeneic tissues. In contrast, cells from other Botryllus' regions do not show comparable stemness capabilities. Cumulatively, these results define the Botryllus' endostyle region as an adult somatic stem cell niche.     

Exercise training enhances baroreflex sensitivity by an angiotensin II-dependent mechanism in chronic heart failure.

Exercise training (EX) has become an important modality capable of enhancing the quality of life and survival of patients with chronic heart failure (CHF). Although 4 wk of EX in animals with CHF evoked a reduction in renal sympathetic nerve activity and ANG II plasma levels and an enhancement in baroreflex sensitivity at rest (Liu JL, Irvine S, Reid IA, Patel KP, Zucker IH, Circulation 102: 1854-1862, 2000; Liu JL, Kulakofsky J, Zucker IH, J Appl Physiol 92: 2403-2408, 2002), it is unclear whether these phenomena are causally related. CHF was induced in rabbits by ventricular pacing (360-380 beats/min) for 3 wk. CHF rabbits were EX for 4 wk at 15-18 m/min, 6 days/wk, 30-40 min/day. Three groups of rabbits were studied: CHF (with no EX), CHF-EX, and CHF-EX + ANG II infusion [in which ANG II levels were kept at or near levels observed in CHF (non-EX) rabbits by subcutaneous osmotic minipump infusion]. EX prevented the increase in plasma ANG II levels shown in CHF rabbits. CHF and CHF-EX + ANG II infusion rabbits had significantly depressed baroreflex sensitivity slopes (P < 0.01 for sodium nitroprusside and P < 0.001 for phenylephrine) and higher baseline renal sympathetic nerve activities than CHF-EX animals. EX downregulated mRNA and protein expression of ANG II type 1 receptors in the rostral ventrolateral medulla in CHF rabbits. This was prevented by ANG II infusion. These data are consistent with the view that the reduction in sympathetic nerve activity and the improvement in baroreflex function in CHF after EX are due to the concomitant reduction in ANG II and angiotensin receptors in the central nervous system.     

Hypoxic induction of UCP3 in the growth plate: UCP3 suppresses chondrocyte autophagy

The overall goal of the investigation was to examine the role of uncoupling proteins (UCPs) in regulating late stage events in the chondrocyte maturation pathway. We showed for the first time that epiphyseal chondrocytes expressed UCP3. In hypoxia, UCP3 mediated regulation of the mitochondrial transmembrane potential (DeltaPsi(m)) was dependent on HIF-1alpha. We also showed for the first time that UCP3 regulated the induction of autophagy. Thus, suppression of UCP3 enhanced the expression of the autophagic phenotype, even in serum-replete media. Predictably, the mature autophagic chondrocytes were susceptible to an apoptogen challenge. Susceptibility was probably associated with a lowered expression of the anti-apoptotic proteins Bcl2 and BCL(xL) and a raised baseline expression of cytochrome c in the cytosol. These changes would serve to promote sensitivity to apoptogens. We conclude that in concert with HIF-1alpha, UCP3 regulates the activity of the mitochondrion by modulating the transmembrane potential. In addition, it inhibits induction of the autophagic response. When this occurs, it suppresses sensitivity to agents that promote chondrocyte deletion from the growth plate.     

Integrating ecology with biogeography using landscape characteristics: a case study of subtidal habitat across continental Australia

Aim We aimed to redress a current limitation of local ecological studies (i.e. piecemeal information on specific taxa) by integrating existing ecological knowledge with quantifiable patterns in primary habitat (i.e. composition, distribution and cover) from local to continental scales. By achieving this aim, we sought to provide a biogeographical framework for the interpretation of variation in the ecology of, and threats to, subtidal rocky landscapes. Location The subtidal rocky coast of continental Australia, with longitudinal comparisons spanning > 4000 km of southern coast (115°03′ E–153°60′ E) between latitudes of 33°05′ S and 35°36′ S, and latitudinal comparisons across 26°40′ S to 37°08′ S of eastern Australia. Methods The frequency and size of patches of major benthic habitat were quantified to indicate contemporary function (ecology) and to establish patterns that may result from contrasting regional‐scale processes (biogeography). This was achieved by quantifying the composition and patchiness of key subtidal habitats across the continent and relating them to the known ecology of subsets of locations in each region. A nested design of several spatial scales (1000s, 100s, 10–1 km) was adopted to distinguish patterns at local through to biogeographical scales. Results We show biogeography (in terms of longitude and latitude) to have a fundamental influence on the patterns of abundance and composition of subtidal habitats across regional (1000s of kilometres) to local (10s of kilometres to metres) scales. Across the continent, the most fundamental patterns related to (1) the proportion of rock covered by kelp forests, as related to particular functional groups of herbivores, and (2) the small‐scale heterogeneity (metres) that characterizes these forests. Main conclusions We interpret these results within a framework of alternative processes known to maintain habitat heterogeneity across these regions (e.g. productivity versus consumption as shapers of habitat structure). These interpretations illustrate how regional differences in ecological patterns and processes can create contradictory outcomes for the management of natural resources. We suggest that researchers and managers of natural resources alike may benefit from understanding local issues (e.g. the effects of fishing and its synergies with water pollution) in their biogeographical contexts.     

Stability ofAlternaria toxins in fruit juices and wine

Alternaria alternata is a common fungal parasite on fruits and other plants and produces a number of mycotoxins, including alternariol (3,7,9-trihydroxy-1-methyl-6H-dibenzo [b,d]pyran-6-one), alternariol monomethyl ether (3,7-dihydroxy-9-methoxy-1-methyl-6H-dibenzo[b,d]pyran-6-one), and the mutagen altertoxin I {[1S-(1α,12aβ,12bα)] 1,2,11,12,12a, 12b-hexahydro-1,4,9,12a-tetrahydroxy-3,10-perylenedione}. Alternariol and alternariol monomethyl ether have previously been detected in some samples of fruit beverages. Stability studies of these toxins as well as altertoxin I added to fruit juices and wine (10–100 ng/mL) were carried out. To include altertoxin I in the analysis, cleanup with a polymer-based Varian Abselut solid phase extraction column was used, as recoveries from C-18 columns were low. The stabilities of alternariol and alternariol monomethyl ether in a low acid apple juice containing no declared vitamin C were compared with those in the same juice containing added vitamin C (60 mg/175 ml); there were no apparent losses at room temperature over 20 days or at 80°C after 20 min. in either juice. Altertoxin I was moderately stable in pH 3 buffer (75% remaining after a two week period). Furthermore, altertoxin I was stable or moderately stable in three brands of apple juice tested over 1–27 day periods and in a sample of red grape juice over 7 days. It is concluded that altertoxin I is sufficiently stable to be found in fruit juices and should be included in methods for alternariol and alternariol monomethyl ether.     

Genotoxicity risk assessment: a proposed classification strategy

Recent advances in genetic toxicity (mutagenicity) testing methods and in approaches to performing risk assessment are prompting a renewed effort to harmonize genotoxicity risk assessment across the world. The US Environmental Protection Agency (EPA) first published Guidelines for Mutagenicity Risk Assessment in 1986 that focused mainly on transmissible germ cell genetic risk. Somatic cell genetic risk has also been a risk consideration, usually in support of carcinogenicity assessments. EPA and other international regulatory bodies have published mutagenicity testing requirements for agents (pesticides, pharmaceuticals, etc.) to generate data for use in genotoxicity risk assessments. The scheme that follows provides a proposed harmonization approach in which genotoxicity assessments are fully developed within the risk assessment paradigm used by EPA, and sets out a process that integrates newer thinking in testing battery design with the risk assessment process. A classification strategy for agents based on inherent genotoxicity, dose-responses observed in the data, and an exposure analysis is proposed. The classification leads to an initial level of concern for genotoxic risk to humans. A total risk characterization is performed using all relevant toxicity data and a comprehensive exposure evaluation in association with the genotoxicity data. The result of this characterization is ultimately used to generate a final level of concern for genotoxic risk to humans. The final level of concern and characterized genotoxicity risk assessment are communicated to decision makers for possible regulatory action(s) and to the public.