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Investigation of organic compounds in ice cores can potentially unlock a wealth of new information in these climate archives. We present results from the first ever ice core drilled on sub‐Antarctic island Bouvet, representing a climatologically important but understudied region. We analyze a suite of novel and more familiar organic compounds in the ice core, alongside commonly measured ions. Methanesulfonic acid shows a significant, positive correlation to winter sea ice concentration, as does a fatty acid compound, oleic acid. Both may be sourced from spring phytoplankton blooms, which are larger following greater sea ice extent in the preceding winter. Oxalate, formate, and acetate are positively correlated to sea ice concentration in summer, but sources of these require further investigation. This study demonstrates the potential application of organic compounds from the marine biosphere in generating multiproxy sea ice records, which is critical in improving our understanding of past sea ice changes. Ice cores are vertical cylinders of ice drilled from an ice sheet, younger at the top and older at the bottom. Particles emitted from plants and animals on land and in the ocean, containing organic chemical compounds, are carried by atmospheric circulation, deposited on the ice surface, and become trapped inside ice layers. They are a record of environmental conditions at the location and time the particles originally formed. Here, we look for a number of these organic compounds in an ice core from Bouvet Island in the sub‐Antarctic. We find the amounts of some are related to amounts of sea ice around the island in the spring. This is because the particles are originally emitted by phytoplankton, for which the amount of sea ice that year controls the amount of phytoplankton (more sea ice in the winter = greater area of sea ice break up in spring = more phytoplankton in spring). We find other organic compounds are related to amounts of sea ice in summer, but their sources are less well known. Combining these records with their relationships to sea ice will be useful in helping us to better understand sea ice changes in the past. We analyzed a suite of organic compounds,alongside commonly measured ions, in the first ever shallow ice core from Bouvet IslandMultiple marine‐sourced organic compounds are detected throughout the coreOrganic compounds, alongside MSA, show significant positive correlations with sea ice

A comparative analysis of the effect of two compounds, dibutyryl–cyclic-AMP (dbcAMP) and latrunculin B, on the morphology and ultrastructure of the dimorphic fungus Mucor rouxiiunder aerobic growth conditions is presented. dbcAMP acts through the sustained activation of protein kinase A, and latrunculin B through the disruption of the actin cytoskeleton. Upon addition of these compounds to the growth medium at any stage of the germination process, cells lost polarised growth and switched to isodiametric growth. The effect was reversible. The morphologies, visualised by light microscopy or scanning electron microscopy (SEM), were alike. A switch from a rough to a smooth surface was observed by SEM when cells were repolarised by removal of the added compound. Ultrastructural changes under both conditions, as observed by transmission electron microscopy, were similar, the main feature being the enlargement of the cell wall, with irregular depositions, and detachment from the cell membrane. dbcAMP-treated cells showed a decrease in the number of glycogen granules compared with control and latrunculin B-treated cells. F-actin staining with fluorescein isothiocyanate–phalloidin showed that both dbcAMP- and latrunculin B-treated cells displayed a much lower fluorescence than control cells, with only a few pale plaques. The results suggest that the sustained activation of protein kinase A, which impairs polarised growth, might exert its effect through a modification of actin cytoskeleton organisation, very probably also involving an integrinlike pathway, as judged by the cell wall detachment and loss of cell adhesiveness of the dbcAMP-treated isodiametric cells.A comparative analysis of the effect of two compounds, dibutyryl–cyclic-AMP (dbcAMP) and latrunculin B, on the morphology and ultrastructure of the dimorphic fungus Mucor rouxiiunder aerobic growth conditions is presented. dbcAMP acts through the sustained activation of protein kinase A, and latrunculin B through the disruption of the actin cytoskeleton. Upon addition of these compounds to the growth medium at any stage of the germination process, cells lost polarised growth and switched to isodiametric growth. The effect was reversible. The morphologies, visualised by light microscopy or scanning electron microscopy (SEM), were alike. A switch from a rough to a smooth surface was observed by SEM when cells were repolarised by removal of the added compound. Ultrastructural changes under both conditions, as observed by transmission electron microscopy, were similar, the main feature being the enlargement of the cell wall, with irregular depositions, and detachment from the cell membrane. dbcAMP-treated cells showed a decrease in the number of glycogen granules compared with control and latrunculin B-treated cells. F-actin staining with fluorescein isothiocyanate–phalloidin showed that both dbcAMP- and latrunculin B-treated cells displayed a much lower fluorescence than control cells, with only a few pale plaques. The results suggest that the sustained activation of protein kinase A, which impairs polarised growth, might exert its effect through a modification of actin cytoskeleton organisation, very probably also involving an integrinlike pathway, as judged by the cell wall detachment and loss of cell adhesiveness of the dbcAMP-treated isodiametric cells.

The ZaP Flow Z-pinch plasma device at the University of Washington produces a small diameter (20-30 mm) dense Z-pinch plasma with typical electron density 1022-1023m-3and ion plus electron temperature 100-200 eV. The plasma is stable, with relatively low magnetic mode activity, for tens of microseconds. This is orders of magnitude longer than predicted by a simple ideal magnetohydrodynamic calculation. The probable stabilizing mechanism is radial shear in the axial plasma flow. The axially flowing Z-pinch is generated with a coaxial accelerator coupled to a pinch assembly chamber. After the pinch assembles a quiescent period occurs, during which the mode activity is significantly reduced. Multichord Doppler shift measurements of impurity lines show a large, sheared flow during the quiescent period and low, uniform flow profiles during periods of high mode activity. The plasma has a sheared axial flow that exceeds the theoretical threshold for stability during the quiescent period and is lower than the threshold during periods of high mode activity. The Z-pinch plasmas are globally stable for 700-2000 times the theoretically predicted kink growth time of a static Z-pinch. The end of the quiescent period corresponds to a decrease in acceleration of plasma and possibly suggests a means to extend the experiment to quasi-steady-state operation.

AbstractAims: To assess the attitudes of Australian doctors towards the use of antithrombotic drug therapy for stroke prevention in patients with non-valvular atrial fibrillation (AF), and investigate the barriers to prescribing warfarin. Methods: A postal survey was undertaken among approximately 10% of all registered general practitioners (GPs), cardiologists and physicians in Australia. The anonymous questionnaire used case scenarios to assess doctors’ knowledge of current guidelines for the therapeutic management of AF and sought opinions on potential barriers to the use of anticoagulation. Results: Completed questionnaires were received from 711 doctors (30% response rate). The GPs performed better than the cardiologists and other specialists in estimating the risk of stroke in case scenarios. However, the cardiologists were more likely to select the recommended treatment, with GPs being more hesitant to use anticoagulation and tending to underestimate its reported benefit for stroke prevention in non-valvular AF. The GPs were also more likely to overestimate the reported risk of major bleeds with warfarin. In contrast, over one-third of the cardiologists went as far as to give warfarin to a low-risk patient and they were more likely to overestimate the reported benefit of aspirin and warfarin in AF. Only half the doctors correctly classified a patient without a previous stroke (but with other risk factors) as being at high risk. Increased experience as a registered medical practitioner was generally related to a poorer performance on classifying patients according to the risk of stroke. The principal barriers to the use of anticoagulation were nominated as: (i) active gastrointestinal bleeding, (ii) previous intracranial haemorrhage, (iii) alcoholism, (iv) a history of daily falls, (v) liver disease, (vi) severe anaemia and (vii) concurrent use of non-steroidal anti-inflammatory drugs. Conclusion: There is scope for improvement in doctors’ knowledge about the appropriate use of antithrombotic drug therapy in non-valvular AF and awareness of the results of recent clinical trials. Compilation and dissemination of clear guidelines and focused education on some of the other risk factors (apart from previous stroke or transient ischaemic attacks) in patients with non-valvular AF are important strategies for targeting barriers to the use of anticoagulation for stroke prevention. (Intern Med J 2002; 32: 15–23)

Background: The benefits of antithrombotic therapy in chronic atrial fibrillation (AF) have been established in clinical trials, but there is a paucity of data on outcomes in practice. Aims: The objective was to establish a large ongoing database of patients with non-valvular AF, to enable the accurate determination of clinical outcomes. Methods: A retrospective review of the medical records for consecutive patients who had AF documented on electrocardiogram at the major teaching hospital in Tasmania between 1 January 1997 and 30 June 1999 was performed. An extensive range of demographic and clinical variables was recorded for all patients with chronic or paroxysmal non-valvular AF. Results: The 505 patients (60% males) included in the database had a median age of 76 years. According to risk stratification criteria, 79% of the patients with previously diagnosed chronic or paroxysmal AF had a high risk of developing stroke at the time of admission to hospital care. However, only one-third (34%) of these patients were receiving warfarin (or warfarin plus aspirin), with almost one-quarter (24%) receiving no antithrombotic agent. The annual incidence of ischaemic strokes was 3.4% (1.5–6.4%; 95% CI) when taking warfarin, compared to 7.0% (5.2–9.4%) for patients not taking warfarin and 7.8% (5.4–11.1%) for patients taking aspirin. The annual incidence of bleeding complications in patients taking warfarin was 14.2% (10.0–19.5%) overall and 3.4% (1.5–6.4%) for major bleeds. In patients not taking warfarin, the overall annual incidence of bleeds was 8.4% (6.3–10.9%) and 3.9% (2.5–5.7%) for major bleeds. Conclusions: Warfarin is underused in patients with AF. In clinical practice, warfarin confers a similar stroke risk reduction to that observed in trials, with an increase in incidence of only minor bleeding complications. Aspirin did not appear to reduce the risk of stroke. (Intern Med J 2001; 31: 329–336)

Abstract: Disseminated peritoneal adenomucinosis (DPAM) is a relatively rare cause of pseudomyxoma peritonei, marked by peritoneal lesions with abundant extracellular mucin and little cytologic atypia among exfoliated tumor cells, and usually associated with appendiceal adenomas. Peritoneal mucinous carcinomatosis (PMCA) also causes diffuse peritoneal tumor but is marked by neoplastic mucinous epithelium with cytologic features of carcinoma and associated with appendiceal, colon, gastric, or small bowel carcinoma. Compared with PMCA, DPAM has a different distribution of disease and a significantly better prognosis. DPAM is characterized by the lack of lymph node involvement, with primarily superficial peritoneal involvement, and a relatively benign, relapsing course over many years. Dominant primary masses may not be evident in DPAM. Despite considerable overlap in the two main causes of pseudomyxoma peritonei, there are features of the two that may help differentiate between them. We present the computed tomographic appearance of DPAM in a series of seven cases and emphasize characteristics of the disease.

Summary Changes in intracellular pH (pHi) have been examined during zoosporogenesis inPhytophthora cinnamomi in order to elucidate the molecular mechanisms that bring about initiation of the orderly cleavage of the sporangium. By microinjecting a dextranconjugated pH-sensitive fluorescent indicator, 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF dextran), and using fluorescence ratio image analysis, the pHi of a sporangium was monitored throughout the process of zoosporogenesis. The pHi of mature sporangia was found to remain constant at pH 6.84 ± 0.05 (mean ± SE, n=6) at room temperature (24 °C), but increased to 7.04 ± 0.04 (p < 0.001) during a 20 min cold treatment at 19 °C. As the process of zoosporogenesis proceeded, the increased level of pHi was maintained for 30–40 min after initiation of the cold shock. Zoosporogenesis was blocked when the pHi of the sporangium was held constant by microinjecting with 10 mM HEPES buffer (pH 7.0) before cytoplasmic cleavage was induced by a cold shock. In contrast, no inhibitory effect was observed when sporangia were microinjected with HEPES buffer after the cold shock. These results indicate that initiation of cytoplasmic cleavage requires a rise in pHi.

Summary A dynamic population of cytoplasmic F-actin was observed with electroporated rhodamine phalloidin (RP) staining in growing hyphae ofSaprolegnia ferax. This central actin population was distinct from the fibrillar peripheral network previously described in chemically fixed hyphae in that it was diffuse, pervaded the entire cytoplasm and was most concentrated in the central cytoplasm 8.4 µm from the tip. The peripheral network did not stain with electroporated RP. The apical concentration of central cytoplasmic actin was only present in growing hyphae and developed prior to tip extension. It co-localized with the polarized distribution of mitochondria and endoplasmic reticulum in the tip, suggesting that it functions in positioning these organelles during tip growth. Within the central actin there was a consistent apical cleft which only occurred in growing hyphae and whose position predicted the direction of tip growth. This cleft was coincident with the known accumulation of apical wall vesicles, suggesting that it is either established by vesicle exclusion of the central actin network or is permeated by a portion of the in vivo unstained peripheral network. Photobleaching studies showed that in both growing and non-growing hyphae, cytoplasmic actin continually and rapidly moved from subapical regions to the tip where it accumulated. It mostly moved forward at the rate of tip growth, while some also left the tip, presumably to populate subapical regions.

A role for Ca2+ in the tip growth process of fungal hyphae and other eukaryotic walled cells has been widely explored, following the earlier indications of their importance by Jaffe, Steer, and their colleagues. Analysis of the literature on fungi, with selected comparison with other tip-growing plant cells, shows that the growth rate and morphology of hyphae are sensitive to factors which influence intracellular Ca2+. These factors include variations in extracellular Ca2+ concentrations, Ca2+ ionophores, inhibitors of Ca2+ transport, and calmodulin- and Ca(2+)-binding dyes and buffers introduced into the cytoplasm. The effects of these agents appear to be mediated by a tip-high gradient of cytoplasmic free Ca2+ which is obligatorily present in all critically examined growing tips. Most recent observations agree that the gradient is very steep, declining rapidly within 10 to 20 microns of the tip. This gradient seems to be generated by the combined effects of an influx of Ca2+, via plasma membrane, possibly stretch-activated, channels localized in the hyphal tip, and subapical expulsion or sequestration of these ions. Expulsion probably involves a plasma membrane Ca(2+)-ATPase, but it is not yet possible to differentiate among mitochondria, endoplasmic reticulum, or vacuoles as the dominant sites of sequestration. It is suggested that regulation of the Ca2+ gradient in turn modulates the properties of the actin-based component of the cytoskeleton, which then controls the extensibility, and, possibly, the synthesis of the hyphal apex. Regulatory feedback mechanisms intrinsic to this model of tip growth regulation are briefly discussed, together with suggestions for future experiments which are crucial to its further elucidation and establishment.