Adv Exp Med Biol
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Nebraska agencies and public health organizations collaboratively addressed cyanobacterial issues for the first time after two dogs died within hours of drinking water from a small private lake south of Omaha on May 4, 2004. A necropsy on one of the dogs revealed that the cause of death was due to ingestion of Microcystin toxins. Within two weeks after the dog deaths, state and local officials jointly developed strategies for monitoring cyanobacterial blooms and issuing public health alerts and advisories. ⋯ Four lakes were on health alert for 12 or more weeks. The primary cyanobacterial bloom-forming genera identified in Nebraska lakes were Anabaena, Aphanizomenon, and Microcystis. Preliminary assessments of lake water quality data indicated that lower lake levels from the recent drought and low nitrogen to phosphorus ratios may have contributed, in part, to the increased numbers of cyanobacterial complaints and problems that occurred in 2004.
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This paper reviews the rapidly expanding literature on the ecological effects of cyanobacterial toxins. The study employs a qualitative meta-analysis from the literature examining results from a large number of independent studies and extracts general patterns from the literature or signals contradictions. The meta-analysis is set up by putting together two large tables--embodying a large and representative part of the literature (see Appendix A). ⋯ The paper concludes by summarizing the risks for birds, fish, macroinvertebrates and zooplankton. Although acute (lethal) effects are mentioned in the literature, mass mortalities of--especially--fish are more likely to be the result of multiple stress factors that co-occur during cyanobacterial blooms. Bivalves appear remarkably resistant, whilst the harmful effects of cyanobacteria on zooplankton vary widely and the specific contribution of toxins is hard to evaluate.
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Dengue is a major global disease which, in its severe form, affects up to 500,000 people worldwide each year, most of whom are children. The development of a safe and effective vaccine is a clear priority, together with public health measures to prevent the spread of infection. However, while major epidemics continue to occur, clinicians must also focus on optimising management. ⋯ Very careful titration of fluid therapy is necessary combined with frequent reassessment for signs of worsening shock or the development of fluid overload. In most DSS cases isotonic crystalloid solutions are as effective as colloid solutions, but the question whether early intervention with colloid solutions improves outcome in more advanced shock requires further investigation. The outcome of studies to address this question, together with further research to examine the pathophysiological mechanisms underlying the plasma leakage, will hopefully result in better management of children with severe dengue but may also provide useful insights into other diseases that affect endothelial function.
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Randomized Controlled Trial
The effect of two different intermittent hypoxia protocols on ventilatory responses to hypoxia and carbon dioxide at rest.
Intermittent hypoxia (IH) consists of bouts of hypoxic exposure interspersed with normoxic intervals. The optimal IH regime for increasing the ventilatory response in humans is unknown, although in animals there is evidence that multiple short duration bouts of intermittent hypoxia (SDIH) provoke larger changes in chemosensitivity than longer duration bouts of intermittent hypoxia (LDIH). The purpose of this study was to compare responses to both hypercapnia and hypoxia between the two protocols. ⋯ Following each 7-day IH protocol, mean HVR was significantly (p < 0.05) increased by 67% and 49% (for LDIH and SDIH, respectively). One week post IH, HVR values were not different from pre-values. HCVR was increased significantly by the LDIH protocol by 44.1% (p < 0.01) and remained elevated by 41.5% at 7 days post (p < 0.01). The changes following the SDIH protocol were smaller (20.7% and 13.5%, at 1 and 7 days post IH, respectively) and not significant. The HCVR remained elevated 7 days following IH (26.7%, p < 0.01). In both the hyperoxic and hypoxic modified rebreathing tests, the CO2 sensitivity was unchanged by either intervention. In hypoxia, the CO2 threshold was significantly reduced following both protocols (p < 0.05). LDIH reduced the threshold by 1.60mmHg, whereas following SDIH it was reduced by 1.98mmHg. Under hyperoxic conditions, LDIH reduced the CO2 threshold by 2.06 mmHg, and SDIH caused a reduction of 2.53 mmHg. There were no significant differences between the two IH protocols for any of the above measures. A 7-day intermittent hypoxic protocol consisting of daily 60-minute exposures to normobaric poikilocapnic hypoxia caused increases in HVR and HCVR. This protocol caused a left-shift in the CO2 threshold but no change in CO2 sensitivity by the modified rebreathing protocol. Neither protocol proved superior in effecting these changes in the resting control of breathing.
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Oxy- (HbO2) and deoxy- (HHb) haemoglobin signals measured by near infrared (NIR) spectroscopy over the human frontal lobes frequently contain respiratory and low frequency oscillations (LFOs). It has been suggested previously that venous oxygen saturation (SvO2) can be calculated from these respiratory oscillations. In this paper, we investigated the use of a Fourier transform based algorithm to calculate an oxygen saturation measure known as S(osc)O2 which may be a close estimate of the underlying SvO2. ⋯ The calculated S(osc)O2 values were compared with other cerebral oxygenation measures including an intraparenchymal catheter based brain tissue oxygen tension (PbrO2) and the NIR based tissue oxygenation index (TOI). It was found that the S(osc)O2 calculated using the combined respiratory and LFO frequency range and the SRS method resulted in the highest detection rates of hyperoxic changes. This measure of S(osc)O2 may provide a viable, continuous, non invasive, bedside measure of cerebral venous oxygen saturation.