Do they stay or do they go? Acoustic monitoring of whale sharks at Ningaloo Marine Park,Western Australia

Whale sharks Rhincodon typus were monitored via acoustic transmitters at the northern end of Western Australia's Ningaloo Marine Park to establish the extent to which the species inhabits the region beyond the whale‐shark ecotourism industry season, which usually extends from March to August in each year. Despite the vast majority (c. 98%) of photographic submissions of R. typus from Ningaloo Reef being between March and August, acoustic detections from the tagged R. typus at Ningaloo were recorded in all months of the year, but do not preclude the occurrence of extended absences. It is concluded that as a species, R. typus occurs year round at Ningaloo, where it generally remains in close proximity to the reef edge, but that some individuals move outside of the detection range of the array for extended periods.     

The timing of hibernation in Tasmanian echidnas: why do they do it when they do?

We investigated the patterns of hibernation and arousals in seven free-ranging echidnas Tachyglossus aculeatus setosus (two male, five female) in Tasmania using implanted temperature data loggers. All echidnas showed a ‘classical’ pattern of mammalian hibernation, with bouts of deep torpor interrupted by periodic arousals to euthermia (mean duration 1.04±0.05 (n=146). Torpor bout length increased as body temperature fell during the hibernation season, and became more variable as temperature rose again. Hibernation started in late summer (February 28±5 days, n=6) and males aroused just before the winter solstice (June 15±3 days, n=3), females that subsequently produced young aroused 40 days later (July 25±3, n=4) while females that did not produce young hibernated for a further two months (arousal Sept 27±5, n=7). We suggest that hibernation in Tasmanian echidnas can be divided into two phases, the first phase, marked by declining minimum body temperatures as ambient temperature falls, appears to be obligatory for all animals, while the second phase is ‘optional’ and is utilised to varying amounts by females. We suggest that early arousal and breeding is the favoured option for females in good condition, and that the ability to completely omit breeding in some years, and hibernate through to spring is an adaptation to an uncertain climate.     

Pleiotropic effects of statins: do they matter?

Treatment with the 3-hydroxy-3-methylglutaryl coenyzme A reductase inhibitors (or statins) reduces the risk for cardiovascular events across a broad spectrum of patient profiles, as evidenced by both primary prevention and secondary prevention trials. Improved survival by way of reduced deaths from coronary heart disease was also reported with these agents, which are primarily indicated for substantial reduction in LDL-cholesterol levels. However, the statins are extremely complex drugs and exhibit a wide variety of vascular effects that may or may not be dependent on their lipid-modifying properties. These so-called pleiotropic effects include alterations of endothelial function, inflammation, coagulation, and plaque stability. The relative contribution of the nonlipid effects of statin therapy to the well-documented clinical benefits is currently under intense investigation.     

Bacterial EPIYA effectors – Where do they come from? What are they? Where are they going?

Recent studies have revealed a distinct class of bacterial effectors defined by the presence of EPIYA or EPIYA‐related motif. These bacterial EPIYA effectors are delivered into host cells via type III or IV secretion, where they undergo tyrosine phosphorylation at the EPIYA motif and thereby manipulate host signalling by promiscuously interacting with multiple SH2 domain‐containing proteins. Up to now, nine EPIYA effectors have been identified from various bacteria. These effectors do not share sequence homology outside the EPIYA motif, arguing against the idea that they have common ancestors. A search of mammalian proteomes revealed the presence of a mammalian EPIYA‐containing protein, Pragmin, which potentiates Src family kinase (SFK) activity by binding and sequestrating the SFK inhibitor Csk upon EPIYA phosphorylation. As several bacterial EPIYA effectors also target Csk, they may have evolved through generation of sequences that mimic the Pragmin EPIYA motif. EPIYA motifs are often diverged through multiple duplications in each bacterial effector. Such a structural plasticity appears to be due to intrinsic disorder of the EPIYA‐containing region, which enables the bacterial effectors to undergo efficient phosphorylation and mediate promiscuous interaction with multiple host proteins. Given the functional versatility of the EPIYA motif, many more bacterial EPIYA effectors will soon be emerging.     

Mechanosensitive channels: what can they do and how do they do it?

While mechanobiological processes employ diverse mechanisms, at their heart are force-induced perturbations in the structure and dynamics of molecules capable of triggering subsequent events. Among the best characterized force-sensing systems are bacterial mechanosensitive channels. These channels reflect an intimate coupling of protein conformation with the mechanics of the surrounding membrane; the membrane serves as an adaptable sensor that responds to an input of applied force and converts it into an output signal, interpreted for the cell by mechanosensitive channels. The cell can exploit this information in a number of ways: ensuring cellular viability in the presence of osmotic stress and perhaps also serving as a signal transducer for membrane tension or other functions. This review focuses on the bacterial mechanosensitive channels of large (MscL) and small (MscS) conductance and their eukaryotic homologs, with an emphasis on the outstanding issues surrounding the function and mechanism of this fascinating class of molecules.     

Bacterial motility: how do pili pull?

Forceful retraction of a bacterial pilus has been directly observed for the first time. As retraction clarifies the basic mechanochemistry of single cell twitching and gliding movements, so cell-to-cell signalling by contact clarifies the coordination of multicellular gliding movements.     

Cytosolic glycosidases: do they exist?

The substrate specificity of the alpha-D-mannosidases of rat liver lysosome and cytosol was examined using oligosaccharides of the oligomannosidic type. The hydrolysis products were characterized by 400 MHz 1H-NMR spectroscopy. Both catabolic pathways occur in ordered ways, but are quite different. In fact, the lysosomal pathway is a two-step process: the first step involves a Zn(2+)-independent alpha-1,2-mannosidase activity, whereas the second involves a Zn(2+)-dependent alpha-1,3- and alpha-1,6-mannosidase activity. The final product is the disaccharide Man(beta 1-4)GlcNAc. In contrast, the cytosolic pathway leads, in one step, to a unique hexasaccharide (Man5GlcNAc) which has the same structure as the polyprenolic intermediate synthesized on the cytosolic face of the rough endoplasmic reticulum during the biosynthesis of N-glycosylprotein glycans: Man(alpha 1-2)-Man(alpha 1-2)Man(alpha 1-3)[Man(alpha 1-6)] Man(beta 1-4)GlcNAc(beta 1-4)-GlcNAc(alpha)P-P-Dol. In addition, the enzymatic parameters of lysosome, endoplasmic reticulum and cytosol alpha-D-mannosidases are quite different. These results lead to the conclusion that the cytosol contains specific alpha-D-mannosidases which do not originate from lysosomes nor from endoplasmic reticulum. The discovery of cytosolic endo-N-acetyl-beta-D-glucosaminidase active on 'immature complex glycans' (glycopeptides of the oligomannosidic type and of the desialylated N-acetyllactosaminic type) as well as on the glycosyl-dolichol pyrophosphate intermediates allows us to hypothesize that these enzymes belong to a control system of N-glycosylprotein biosynthesis, their role being to destroy unfinished glycans. The fate of the formed oligosaccharide structures is discussed: are they destroyed by cytosolic or lysosomal exoglycosidases, or do they carry an 'oligosaccharin-like activity'?     

Pathogenic archaea: do they exist?

Archaea are microorganisms that are distinct from bacteria and eukaryotes. They are prevalent in extreme environments, and yet found in most ecosystems. They are a natural component of the microbiota of most, if not all, humans and other animals. Despite their ubiquity and close association with humans, animals and plants, no pathogenic archaea have been identified. Because no archaeal pathogens have yet been identified, there is a general assumption that archaeal pathogens do not exist. This review examines whether this is a good assumption by investigating the potential for archaea to be or become pathogens. This is achieved by addressing: the diversity of archaea versus known pathogens, opportunities for archaea to demonstrate pathogenicity and be detected as pathogens, reports linking archaea with disease, and immune responses to archaea. In addition, molecular and genomic data are examined for the presence of systems utilised in pathogenesis. The view of this report is that, although archaea can presently be described as non-pathogenic, they have the potential to be (discovered as) pathogens. The present optimistic view that there are no archaeal pathogens is tainted by a severe lack of relevant knowledge, which may have important consequences in the future.     

Stress management techniques: Are they all equivalent,or do they have specific effects?

This article evaluates the hypothesis that various stress management techniques have specific effects. Studies comparing various techniques are reviewed, as well as previous literature reviews evaluating the effects of individual techniques. There is evidence that cognitively oriented methods have specific cognitive effects, that specific autonomic effects result from autonomically oriented methods, and that specific muscular effects are produced by muscularly oriented methods. Muscle relaxation and/or EMG biofeedback have greater muscular effects and smaller autonomic effects than finger temperature biofeedback and/or autogenic training. EMG biofeedback produces greater effects on particular muscular groups than progressive relaxation, and thermal biofeedback has greater finger temperature effects than autogenic training. Disorders with a predominant muscular component (e.g., tension headaches) are treated more effectively by muscularly oriented methods, while disorders in which autonomic dysfunction predominates (e.g., hypertension, migraine headaches) are more effectively treated by techniques with a strong autonomic component. Anxiety and phobias tend to be most effectively treated by methods with both strong cognitive and behavioral components.This work was supported by grants Nos. HL-34336 and HL-44097 from the Heart, Lung, and Blood Institute of the National Institutes of Health. Material in this article has been condensed and updated from three chapters in Lehrer, P. M., and Woolfolk, R. L. (1993).Principles and practice of stress management, Vol. 2, New York: Guilford Press.     

Pathogen effectors: What do they do at plasmodesmata?

Plants perceive an assortment of external cues during their life cycle, including abiotic and biotic stressors. Biotic stress from a variety of pathogens, including viruses, oomycetes, fungi, and bacteria, is considered to be a substantial factor hindering plant growth and development. To hijack the host cell's defence machinery, plant pathogens have evolved sophisticated attack strategies mediated by numerous effector proteins. Several studies have indicated that plasmodesmata (PD), symplasmic pores that facilitate cell-to-cell communication between a cell and neighbouring cells, are one of the targets of pathogen effectors. However, in contrast to plant-pathogenic viruses, reports of fungal- and bacterial-encoded effectors that localize to and exploit PD are limited. Surprisingly, a recent study of PD-associated bacterial effectors has shown that a number of bacterial effectors undergo cell-to-cell movement via PD. Here we summarize and highlight recent advances in the study of PD-associated fungal/oomycete/bacterial effectors. We also discuss how pathogen effectors interfere with host defence mechanisms in the context of PD regulation.     

Potassium channel structures: do they conform?

Potassium channels are signalling elements vital to vertebrate neurotransmission, and cardiac and renal function. Two inherent qualities equip them for their role in the interconversion of chemical and electrical messages: high selectivity for potassium ions and the ability to open (gate) on cue. The crystal structure of KcsA, published in 1998, explained much about potassium selectivity and high ion flux. The enormous diversity of potassium channels (some hundreds of genes in humans) may have hampered similar progress in understanding gating processes. The recent determination of several representative structures has provided us with a valuable reference for discriminating between features that are utilized in gating across the potassium channel genre and features that determine responsiveness to family-specific gating cues.     

Use of periodic abstinence in Bangladesh: do they really understand?

Data from a nationally representative study in Bangladesh (BDHS 1996-97) were analysed to identify significant predictors of use of periodic abstinence, in comparison with other modern contraceptive methods. The study found that women in Bangladesh mostly use modern methods during their peak reproductive years, after which some of them switch to periodic abstinence. These women tend to be more from educated and from higher socioeconomic backgrounds and with at least one living son. Another set of data from the Matlab DSS was analysed and the results were in the same direction. Focus group discussions found that women were using the periodic abstinence method incorrectly, abstaining for more days than is necessary. For Bangladeshi contraceptive users to reach a higher degree of use-effectiveness for period abstinence, more IEC materials need to be developed.