The Australian mulga snake (Pseudechis australis: Elapidae): report of a large case series of bites and review of current knowledge.

BACKGROUND: The mulga snake (Pseudechis australis) is the largest terrestrial venomous snake in Australia. It is capable of inflicting severe and occasionally fatal envenoming, but there have been few studies of P. australis bites. OBJECTIVES: To highlight and reinforce the main features of P. australis envenoming and to provide a clearer picture of the epidemiology of bites from this species. METHODS: Selected case records kept by the Toxinology Dept. (Women's and Children's Hospital, Adelaide, Australia) were reviewed retrospectively to determine definite P. australis bites. INCLUSION CRITERIA: definite cases where the snake was identified by a competent person and/or lab specimens (bite site/urine) tested positive for "black snake" using CSL snake venom detection kit in a locality within the known range of P. australis, but without sympatry with other Pseudechis spp. EXCLUSION CRITERIA: where the snake could not be clearly identified under criteria above. Epidemiological and clinical information was recorded and analysed for the definite cases. RESULTS: A total of 27 cases were identified as definite P. australis bites; there were no fatalities. The median age was 35.5 years (IQR 51-23) and 80% of bites occurred in males. More bites occurred in the warmer months (Dec-March) and in those handling/interfering with snakes. Seven people were bitten whilst asleep at night. 21/27 patients developed systemic envenoming (based on signs, symptoms and laboratory results) and 17 cases received antivenom. Local bite site pain (18) and swelling (17) were common as were non-specific generalised symptoms such as nausea, vomiting and headache. Myotoxicity (11) and anticoagulant coagulopathy (10) occurred frequently; haemolysis was seen in fewer cases (3). Two patients developed local tissue injury around the bite site requiring further treatment. CONCLUSIONS: This study confirms previous reports about P. australis bites with respect to high rates of envenoming, commonly associated with pain and swelling and systemic effects of rhabdomyolysis and anticoagulant coagulopathy. Systemic envenoming, even severe cases, responds well to antivenom therapy. Compared to other Australian snakes, a high proportion of bites occur in people asleep at night. Medically significant local tissue injury around the bite site may occur and may be associated with inappropriate first-aid, particularly the vascular occlusive type.

Up-regulation of key microRNAs, and inverse down-regulation of their predicted oxidative phosphorylation target genes, during aging in mouse brain.

Although significant advances have been made in the study of the molecular mechanisms controlling brain aging, post-transcriptional gene regulation in normal brain aging has yet to be explored. Our lab recently reported that predominant microRNA up-regulation is observed in liver during aging, with key microRNAs predicted to target detoxification genes. Here we examine the role of microRNA regulation in brain during the normal aging process. MicroRNA microarrays and global proteomic profiling were used to compare the brain tissues of 10-, 18-, 24-, and 33-month-old mice. Our results suggest that: (1) like liver, during aging the brain exhibits predominant microRNA up-regulation, and this trend starts in mid-life; (2) of the 70 up-regulated microRNAs, 27 are predicted to target 10 genes of mitochondrial complexes III, IV, and F0F1-ATPase, which exhibit inversely correlated expression; (3) mice of extreme longevity (33-month old) exhibit fewer microRNA expression changes from 10-month-old levels than do old adult mice (24-month old). We found unique de-regulated microRNAs shared between aging brain and aging liver, as well as brain- vs. liver-specific microRNAs during normal aging.

Outer membrane-associated serine protease involved in adhesion of Shewanella oneidensis to Fe(III) oxides.

The facultative anaerobe Shewanella oneidensis MR-1 respires a variety of anaerobic electron acceptors, including insoluble Fe(III) oxides. S. oneidensis employs a number of novel strategies for respiration of insoluble Fe(III) oxides, including localization of respiratory proteins to the cell outer membrane (OM). The molecular mechanism by which S. oneidensis adheres to and respires Fe(III) oxides, however, remains poorly understood. In the present study, whole cell fractionation and MALDI-TOF-MS/MS techniques were combined to identify a serine protease (SO3800) associated with the S. oneidensis OM. SO3800 contained predicted structural motifs similar to cell surface-associated serine proteases that function as bacterial adhesins in other gram-negative bacteria. The gene encoding SO3800 was deleted from the S. oneidensis genome, and the resulting mutant strain (DeltaSO3800) was tested for its ability to adhere to and respire Fe(III) oxides. DeltaSO3800 was severely impaired in its ability to adhere to Fe(III) oxides, yet retained wild-type Fe(III) respiratory capability. Laser Doppler velocimetry and cryoetch high-resolution SEM experiments indicated that DeltaSO3800 displayed a lower cell surface charge and higher amount of surface-associated exopolysaccharides. Results of this study indicate that S. oneidensis may respire insoluble Fe(III) oxides at a distance, negating the requirement for attachment prior to electron transfer.

MicroRNA regulation in Ames dwarf mouse liver may contribute to delayed aging.

The Ames dwarf mouse is well known for its remarkable propensity to delay the onset of aging. Although significant advances have been made demonstrating that this aging phenotype results primarily from an endocrine imbalance, the post-transcriptional regulation of gene expression and its impact on longevity remains to be explored. Towards this end, we present the first comprehensive study by microRNA (miRNA) microarray screening to identify dwarf-specific lead miRNAs, and investigate their roles as pivotal molecular regulators directing the long-lived phenotype. Mapping the signature miRNAs to the inversely expressed putative target genes, followed by in situ immunohistochemical staining and in vitro correlation assays, reveals that dwarf mice post-transcriptionally regulate key proteins of intermediate metabolism, most importantly the biosynthetic pathway involving ornithine decarboxylase and spermidine synthase. Functional assays using 3'-untranslated region reporter constructs in co-transfection experiments confirm that miRNA-27a indeed suppresses the expression of both of these proteins, marking them as probable targets of this miRNA in vivo. Moreover, the putative repressed action of this miRNA on ornithine decarboxylase is identified in dwarf mouse liver as early as 2 months of age. Taken together, our results show that among the altered aspects of intermediate metabolism detected in the dwarf mouse liver--glutathione metabolism, the urea cycle and polyamine biosynthesis--miRNA-27a is a key post-transcriptional control. Furthermore, compared to its normal siblings, the dwarf mouse exhibits a head start in regulating these pathways to control their normality, which may ultimately contribute to its extended health-span and longevity.

Epigenetic Control of MicroRNA Expression and Aging.

MicroRNAs are a major category among the noncoding RNA fraction that negatively regulate gene expression at the post-transcriptional level, by either degrading the target messages or inhibiting their translation. MicroRNAs may be referred to as 'dimmer switches' of gene expression, because of their ability to repress gene expression without completely silencing it. Whether through up-regulating specific groups of microRNAs to suppress unwanted gene expressions, or by down-regulating other microRNAs whose target genes' expression is necessary for cellular function, such as cell proliferation, apoptosis, or differentiation, these regulatory RNAs play pivotal roles in a wide variety of cellular processes. The equilibrium between these two groups of microRNA expressions largely determines the function of particular cell types. Our recent results with several model systems show that upon aging, there is a trend of up-regulation of microRNA expression, with concomitant inverse down-regulation of target genes. This review addresses molecular mechanisms that may provide the underlying control for this up-regulating trend, focusing on activation by various microRNAs' own promoters, through binding with pivotal transcription factors, stress response, methylation of clustered DNA domains, etc. Thus, epigenomic control of aging may be due in part to heightened promoter activation of unwanted microRNA expressions, which in turn down-regulate their target gene products. Overriding and dampening the activation of these noncoding RNAs may prove to be a new frontier for future research, to delay aging and extend healthy life-span.

The impact of noncoding RNA on the biochemical and molecular mechanisms of aging.

As the molecular mechanisms associated with aging become more understood, it is apparent that the normal processes involved in the development and metabolism of an organism are subject to changes that upset its crucial homeostatic balance, which in turn sets in motion the weakening and disease-prone process of senescence. This imbalance is the result of a variety of effectors, such as environmental insults, endogenous toxins, and genetic mishaps. In addition, it is highly probable that posttranscriptional regulatory events play a large role in the changes associated with aging. The emerging knowledge of posttranscriptional regulation is redefining our understanding of the complexities of cellular systems biology and genetics. The implications of the impact that small regulatory RNAs have on the many facets of developmental and molecular biology should be included as part of our current understanding of the biochemistry involved in these processes. These molecular regulators-along with other epigenetic events-restrict the flow of genetic expression, thus affording the cell an adjustable and tempered homeostatic balance control. Recent findings in the fields of organismal development, cancer, and aging indicate that small noncoding RNA plays a greater role than previously believed in orchestrating the changes associated with these processes. Furthermore, any misappropriations of these regulatory resources could lead to age-related diseases, and are therefore promising targets for prophylactics and therapeutics to combat maladies associated with aging. Here we report a brief overview of noncoding RNA as well as the potential roles of microRNAs in biochemical equilibriums where imbalance contributes to the many phenotypes of aging.

Terminal electron acceptors influence the quantity and chemical composition of capsular exopolymers produced by anaerobically growing Shewanella spp.

Bacterial exopolymers perform various roles, including acting as a carbon sink, a protective layer against desiccation or antimicrobial agents, or a structural matrix in biofilms. Despite such varied roles, little is known about the heterogeneity of bacterial exopolymer production under varying growth conditions. Here we describe experiments designed to characterize the quantity and quality of exopolymers produced by two commonly studied members of the widely distributed genus Shewanella. Electrokinetic, spectroscopic, and electron microscopic techniques were employed to demonstrate that cell surfaces of Shewanella oneidensis MR-1 (electrophoretic softness, lambda(-1), range from 0.4 to 2.6 nm) are associated with less extracellular polymeric material than surfaces of Shewanella putrefaciens 200R (lambda(-1) range from 1.6 to 3.0 nm). Both species exhibit similar responses to changes in electron acceptor with nitrate- and fumarate-grown cells producing relatively little exopolymer compared to trimethylamine N-oxide (TMAO)-grown cells. In S. oneidensis, the increase in exopolymers has no apparent effect upon cell-surface fixed charge density (-7.7 to -8.7 mM), but for S. putrefaciens a significant drop in fixed charge density is observed between fumarate/nitrate-grown cells (-43 mM) and TMAO-grown cells (-20.8 mM). For both species, exopolymers produced during growth on TMAO have significant amide functionality, increasing from approximately 20-25% of C-containing moieties in nitrate-grown cells to over 30% for TMAO-grown cells (determined from X-ray photoelectron spectroscopy). The increased exopolymer layer associated with TMAO-grown cells appears as a continuous, convoluted layer covering the entire cell surface when viewed by low-temperature, high-resolution scanning electron microscopy. Such significant changes in cell-surface architecture, dependent upon the electron acceptor used for growth, are likely to influence a variety of cell interactions, including aggregation and attachment to surfaces, and the binding of aqueous metal species.