The electrochemical synthesis of hetero7helicenes including pyrrole and furan rings has been established. A single electrochemical operation led to an oxidative heterocoupling and dehydrative ...cyclization sequence to afford oxaza7helicenes in 50–86% yields with 45–77% Faradic efficiencies. Their derivatization and chiroptical properties were also investigated.
Summary Background & aims Age-related physiological changes predispose even the healthy older adult to fluid and electrolyte abnormalities which can cause morbidity and mortality. The aim of this ...narrative review is to highlight key aspects of age-related pathophysiological changes that affect fluid and electrolyte balance in older adults and underpin their importance in the perioperative period. Methods The Web of Science, MEDLINE, PubMed and Google Scholar databases were searched using key terms for relevant studies published in English on fluid balance in older adults during the 15 years preceding June 2013. Randomised controlled trials and large cohort studies were sought; other studies were used when these were not available. The bibliographies of extracted papers were also searched for relevant articles. Results Older adults are susceptible to dehydration and electrolyte abnormalities, with causes ranging from physical disability restricting access to fluid intake to iatrogenic causes including polypharmacy and unmonitored diuretic usage. Renal senescence, as well as physical and mental decline, increase this susceptibility. Older adults are also predisposed to water retention and related electrolyte abnormalities, exacerbated at times of physiological stress. Positive fluid balance has been shown to be an independent risk factor for morbidity and mortality in critically ill patients with acute kidney injury. Conclusions Age-related pathophysiological changes in the handling of fluid and electrolytes make older adults undergoing surgery a high-risk group and an understanding of these changes will enable better management of fluid and electrolyte therapy in the older adult.
World Health Organization rehydration management guidelines (plan C) for severe dehydration are widely practiced in resource-poor settings, but never formally evaluated in a trial. The Fluid ...Expansion as a Supportive Therapy trial raised concerns regarding the safety of bolus therapy for septic shock, warranting a formal evaluation of rehydration therapy for gastroenteritis.
A multi-centre open-label phase II randomised controlled trial evaluated two rehydration strategies in 122 Ugandan/Kenyan children aged 60 days to 12 years with severe dehydration secondary to gastroenteritis. We compared the safety and efficacy of standard rapid rehydration using Ringer's lactate (100 ml/kg over 3 h (6 h if < 1 year), incorporating 0.9% saline boluses for children with shock (plan C) versus slower rehydration: 100 ml/kg Ringer's lactate over 8 h (all ages) without boluses (slow: experimental). The primary outcome was the frequency of serious adverse events (SAE) within 48 h including cardiovascular, respiratory and neurological complications. Secondary outcomes included clinical, biochemical and physiological measures of response to treatment by intravenous rehydration.
One hundred twenty-two eligible children (median (IQR) age 8 (6-12) months) were randomised to plan C (n = 61) or slow (n = 61), with two (2%) lost to follow-up at day 7). Following randomisation mean (SD) time to start intravenous rehydration started was 15 min (18) in both arms. Mean (SD) fluid received by 1 hour was greater in plan C (mean 20.2 ml/kg (12.2) and 33.1 ml/kg (17) for children < 1 year and >- 1 year respectively) versus 10.4 ml/kg (6.6) in slow arm. By 8 hours volume received were similar mean (SD) plan C: 96.3 ml/kg (15.6) and 97.8 ml/kg (10.0) for children < 1 and ≥ 1 year respectively vs 93.2 ml/kg (12.2) in slow arm. By 48-h, three (5%) plan C vs two (3%) slow had an SAE (risk ratio 0.67, 95% CI 0.12-3.85, p = 0.65). There was no difference in time to the correction of dehydration (p = 0.9) or time to discharge (p = 0.8) between groups. Atrial natriuretic peptide levels rose substantially by 8 hours in both arms, which persisted to day 7. Day 7 weights suggested only 33 (29%) could be retrospectively classified as severely dehydration (≥ 10% weight loss).
Slower rehydration over 8 hours appears to be safe, easier to implement than plan C. Future large trials with mortality as the primary endpoint are warranted.
ISRCTN67518332 . Date applied 31 August 2016.
A domino aldol-Ssub.NAr-dehydration 3+3 annulation strategy has been utilized to fuse six-membered cyclic amides onto aromatic substrates. 2-Arylacetamides have been reacted with 2-fluorobenzaldehyde ...derivatives activated toward Ssub.NAr reaction by an electron-withdrawing substituent (NOsub.2, CN, CFsub.3, COsub.2Me) at C5 to prepare 3,6-disubstituted quinolin-2(1H)-ones. Additionally, 3-substituted 1,8-naphthyridin-2(1H)-ones have been similarly derived from 2-fluoronicotinaldehyde. Fifteen examples are reported, and two possible mechanistic scenarios are presented and discussed.
Extreme high environmental temperatures produce a variety of consequences for wildlife, including mass die-offs. Heat waves are increasing in frequency, intensity, and extent, and are projected to ...increase further under climate change. However, the spatial and temporal dynamics of die-off risk are poorly understood. Here, we examine the effects of heat waves on evaporative water loss (EWL) and survival in five desert passerine birds across the southwestern United States using a combination of physiological data, mechanistically informed models, and hourly geospatial temperature data. We ask how rates of EWL vary with temperature across species; how frequently, over what areas, and how rapidly lethal dehydration occurs; how EWL and die-off risk vary with body mass; and how die-off risk is affected by climate warming. We find that smaller-bodied passerines are subject to higher rates of mass-specific EWL than larger-bodied counterparts and thus encounter potentially lethal conditions much more frequently, over shorter daily intervals, and over larger geographic areas. Warming by 4 °C greatly expands the extent, frequency, and intensity of dehydration risk, and introduces new threats for larger passerine birds, particularly those with limited geographic ranges. Our models reveal that increasing air temperatures and heat wave occurrence will potentially have important impacts on the water balance, daily activity, and geographic distribution of arid-zone birds. Impacts may be exacerbated by chronic effects and interactions with other environmental changes. This work underscores the importance of acute risks of high temperatures, particularly for small-bodied species, and suggests conservation of thermal refugia and water sources.
Exercising in the heat induces thermoregulatory and other physiological strain that can lead to impairments in endurance exercise capacity. The purpose of this consensus statement is to provide ...up‐to‐date recommendations to optimize performance during sporting activities undertaken in hot ambient conditions. The most important intervention one can adopt to reduce physiological strain and optimize performance is to heat acclimatize. Heat acclimatization should comprise repeated exercise‐heat exposures over 1–2 weeks. In addition, athletes should initiate competition and training in a euhydrated state and minimize dehydration during exercise. Following the development of commercial cooling systems (e.g., cooling vest), athletes can implement cooling strategies to facilitate heat loss or increase heat storage capacity before training or competing in the heat. Moreover, event organizers should plan for large shaded areas, along with cooling and rehydration facilities, and schedule events in accordance with minimizing the health risks of athletes, especially in mass participation events and during the first hot days of the year. Following the recent examples of the 2008 Olympics and the 2014 FIFA World Cup, sport governing bodies should consider allowing additional (or longer) recovery periods between and during events for hydration and body cooling opportunities when competitions are held in the heat.
Water plays a key role in shaping our planet and making life possible. Given the abundance of water on Earth’s surface and in its interior, chemical reactions involving water, namely hydration and ...dehydration reactions, feature prominently in nature and are critical to the complex set of geochemical and biochemical reactions that make our planet unique. This paper highlights some fundamental aspects of hydration and dehydration reactions in the solid Earth, biology, and man-made materials, as well as their connections to carbon cycling on our planet.
Climate change is negatively affecting many species. The increase in mean air temperature is often associated with shifts in distribution, changes in phenology, and local extinctions. Other factors ...that only partially correlate with air temperature, like water shortage, may also contribute to the negative consequences of climate change. Although the effect of temperature on lizards' ecophysiology is highly studied, many lizards are also at risks of increased water loss and dehydration, which are predicted to increase under climate change. Here we aimed for the first time to explore if lacertid lizards exposed to dehydration thermoregulate less precisely than hydrated lizards and if dehydrated lizards are less active, change the daily pattern of thermoregulation and balance water balance against thermoregulation. We exposed four lizard species with differences in the thermal preference to thermal gradients with or without a source of water. We measured preferred body temperatures, daily pattern of thermoregulation, and the use of space. Dehydration negatively affected thermoregulation in all investigated species. Dehydrated lizards reduced their preferred body temperature and showed a species-specific pattern of hourly change in thermal preference. Furthermore, they more frequently used the colder parts of the gradients and spent more time hidden. Lizards experiencing dehydration may suffer a reduction in survival and fitness because of poor thermoregulation. Similarly, they may spend more time hidden, waiting for more favourable weather conditions. Such inactivity may carry ecological costs especially in those regions that undergo either short or prolonged periods of droughts.
Because the assumption that small changes in hydration status are readily compensated by homeostatic mechanisms has been little studied, the influence of hypohydration on cognition was examined.
We ...assessed whether a loss of <1% of body mass due to hypohydration adversely influenced cognition, and examined the possible underlying mechanisms.
A total of 101 individuals were subjected to a temperature of 30°C for 4 h and randomly either did or did not consume 300 mL H2O during that period. Changes in body mass, urine osmolality, body temperature, and thirst were monitored. Episodic memory, focused attention, mood, and the perceived difficulty of tasks were measured on 3 occasions. The data were analyzed with the use of a regression-based approach whereby we looked for variables that mediated the influence of hypohydration on psychological functioning.
Drinking water improved memory and focused attention. In the short-term, thirst was associated with poorer memory. Later, a greater loss of body mass was associated with poorer memory and attention (mean loss: 0.72%). At 90 min, an increase in thirst was associated with a decline in subjective energy and increased anxiety and depression, effects that were reduced by drinking water. At 180 min, subjects found the tests easier if they had consumed water.
Drinking water was shown, for the first time to our knowledge, to benefit cognitive functioning when there was a loss of <1% body mass at levels that may occur during everyday living. Establishing the variables that generate optimal fluid consumption will help to tailor individual advice, particularly in clinical situations. This trial was registered at clinicaltrials.gov as NCT02671149.
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