Water deprivation and the double- depletion hypothesis: common neural mechanisms underlie thirst and salt appetite

Water deprivation-induced thirst is explained by the double-depletion hypothesis, which predicts that dehydration of the two major body fluid compartments, the extracellular and intracellular compartments, activates signals that combine centrally to induce water intake. However, sodium appetite is also elicited by water deprivation. In this brief review, we stress the importance of the water-depletion and partial extracellular fluid-repletion protocol which permits the distinction between sodium appetite and thirst. Consistent enhancement or a de novo production of sodium intake induced by deactivation of inhibitory nuclei (e.g., lateral parabrachial nucleus) or hormones (oxytocin, atrial natriuretic peptide), in water-deprived, extracellular-dehydrated or, contrary to tradition, intracellular-dehydrated rats, suggests that sodium appetite and thirst share more mechanisms than previously thought. Water deprivation has physiological and health effects in humans that might be related to the salt craving shown by our species.

Lesions of the commissural subnucleus of the nucleus of the solitary tract increase isoproterenol-induced water intake

The nucleus of the solitary tract (NTS) is the primary site of the cardiovascular afferent information about arterial blood pressure and volume. The NTS projects to areas in the central nervous system involved in cardiovascular regulation and hydroelectrolyte balance, such as the anteroventral third ventricle region and the lateral parabrachial nucleus. The aim of the present study was to investigate the effects of electrolytic lesion of the commissural NTS on water and 0.3 M NaCl intake and the cardiovascular responses to subcutaneous injection of isoproterenol. Male Holtzman rats weighing 280 to 320 g were submitted to sham lesion or electrolytic lesion of the commissural NTS (N = 6-15/group). The sham-lesioned rats had the electrode placed along the same coordinates, except that no current was passed. Water intake induced by subcutaneous isoproterenol (30 µg/kg body weight) significantly increased in chronic (15 days) commissural NTS-lesioned rats (to 2.4 ± 0.2 vs sham: 1.9 ± 0.2 mL 100 g body weight-1 60 min-1). Isoproterenol did not induce any sodium intake in sham or in commissural NTS-lesioned rats. The isoproterenol-induced hypotension (sham: -27 ± 4 vs commissural NTS-lesioned rats: -22 ± 4 mmHg/20 min) and tachycardia (sham: 168 ± 10 vs commissural NTS: 144 ± 24 bpm/20 min) were not different between groups. The present results suggest that the commissural NTS is part of an inhibitory neural pathway involved in the control of water intake induced by subcutaneous isoproterenol, and that the overdrinking observed in lesioned rats is not the result of a cardiovascular imbalance in these animals.

Fetal development of regulatory mechanisms for body fluid homeostasis

The balance of body fluids is critical to health and the development of diseases. Although quite a few review papers have shown that several mechanisms, including hormonal and behavioral regulation, play an important role in body fluid homeostasis in adults, there is limited information on the development of regulatory mechanisms for fetal body fluid balance. Hormonal, renal, and behavioral control of body fluids function to some extent in utero. Hormonal mechanisms including the renin-angiotensin system, aldosterone, and vasopressin are involved in modifying fetal renal excretion, reabsorption of sodium and water, and regulation of vascular volume. In utero behavioral changes, such as fetal swallowing, have been suggested to be early functional development in response to dipsogens. Since diseases, such as hypertension, can be traced to fetal origin, it is important to understand the development of fetal regulatory mechanisms for body fluid homeostasis in this early stage of life. This review focuses on fetal hormonal, behavioral, and renal development related to regulation of body fluids in utero.

Role of α2-adrenoceptors in the lateral parabrachial nucleus in the control of body fluid homeostasis

Central α2-adrenoceptors and the pontine lateral parabrachial nucleus (LPBN) are involved in the control of sodium and water intake. Bilateral injections of moxonidine (α2-adrenergic/imidazoline receptor agonist) or noradrenaline into the LPBN strongly increases 0.3 M NaCl intake induced by a combined treatment of furosemide plus captopril. Injection of moxonidine into the LPBN also increases hypertonic NaCl and water intake and reduces oxytocin secretion, urinary sodium, and water excreted by cell-dehydrated rats, causing a positive sodium and water balance, which suggests that moxonidine injected into the LPBN deactivates mechanisms that restrain body fluid volume expansion. Pretreatment with specific α2-adrenoceptor antagonists injected into the LPBN abolishes the behavioral and renal effects of moxonidine or noradrenaline injected into the same area, suggesting that these effects depend on activation of LPBN α2-adrenoceptors. In fluid-depleted rats, the palatability of sodium is reduced by ingestion of hypertonic NaCl, limiting intake. However, in rats treated with moxonidine injected into the LPBN, the NaCl palatability remains high, even after ingestion of significant amounts of 0.3 M NaCl. The changes in behavioral and renal responses produced by activation of α2-adrenoceptors in the LPBN are probably a consequence of reduction of oxytocin secretion and blockade of inhibitory signals that affect sodium palatability. In this review, a model is proposed to show how activation of α2-adrenoceptors in the LPBN may affect palatability and, consequently, ingestion of sodium as well as renal sodium excretion.

The last resort : spa therapy and the docile body in Victorian St. Catharines /

By relying on existing cultural models, the Victorian spa promoted health and wellness. Advertising, together with other forms of promotion, strengthened the legitimacy of its claims to cure a variety of health problems. By the use of some links to science and a mystical folk belief about the efficacy of the local mineral waters, three spas emerged in St.Catharines: the Stephenson House, the WeIland House, and the Springbank. As the twentieth century approached, the spa movement declined and institutionalized medicine struggled to establish a monopoly on health care. This thesis argues that the health spas in St. Catharines occupied that transitional space in nineteenth century medicine between home remedy and hospital. The interplay between scientific discovery and business enterprise produced a climate in which the Victorian health resort flourished. This phenomenon, combined with the various maladies brought on by industrialization, nineteenth-century lifestyle, and the absence of medical options, created a surge in the popularity of health spas and mineral spring therapies. By the tum of the twentieth century, interest in mineral water treatments had declined. The health resorts that had blossomed between 1850 and 1899 began to experience a serious decrease in business. This popular movement became outmoded in the face of emerging medical and scientific knowledge. In St. Catharines, the last resort to remain standing, the WeIland House, finished out the city's spa era as a hospital.

Salinity Intrusion and Seasonal Water Quality Variations in the Tidal Canals of Cochin

The study conducted on the salinity intrusion and seasonal water quality variations in the tidal canals of cochin. The main objectives are, salinity intrusion profile, water quality variation of the surface water of the canals,hierarchical utility of the water bodies and to understand the non-conservative components in the water body. The parameters monitored werepH,temperature,alkalinity,conductivity,DO(dissolvedoxygen),COD(chemical oxygen demand),BOD(biochemical oxygen demand0,chloride, total hardness, calcium hardness, dissolved phosphate, nitrate, total iron, sulphate, turbidity, total coliform and SUVA at 254nm. The tidal canals of GCDA were found to be creeks extending to the interior, canals inter connecting parts of the estuary or canals with seasonally broken segments. Based on utility the canals could be classified as: canals heavely polluted and very saline,canals polluted by urban waste , canals having fresh water for most part of the year and not much polluted, fresh water bodies heavily polluted. During the rainy months carbon fixation by plankton is nonexistent,and during the dry months Chitrapuzha becomes a sink of phosphate. The study indicated abiotic subrouts for dissolved phosphate and revealed the potential pitfalls in LOICZ modeling exercise on sewage ladentidal canals. It was also found that all canals except for the canals of West cochin and chittoorpuzha have fresh water for some part of the year. The water quality index in the durable fresh water stretches was found to be of below average category.

Increased prevalence of indicator and pathogenic bacteria in Vembanadu Lake: a function of salt water regulator, along south west coast of India

Prevalence of faecal indicator bacteria, Escherichia coli and pathogenic bacteria, Vibrio cholerae, Vibrio parahaemolyticus and Salmonella were analysed in Vembanadu lake (98350N 768250E), along south west coast of India for a period of one year from ten stations on the southern and northern sides of a salt water regulator constructed in Vembanadu Lake in order to prevent incursion of seawater during certain periods of the year. While the northern side of the lake has a connection to the sea, the southern side is enclosed when the salt water regulator is closed. The results revealed the water body is polluted with high faecal coliform bacteria with mean MPN value ranging from 1718-7706/100 ml. E. coli, V. cholerae, V. parahaemolyticus and Salmonella serotypes such as S. paratyphi A, B, C and S. newport were isolated and this is the first report on the isolation of these Salmonella serovars from this lake. E. coli showed highest percentage of incidence (85.6–86.7%) followed by Salmonella (42–57%), V. choleare (40–45%) and V. parahaemolyticus (31.5–32%). The increased prevalence of indicator and pathogenic bacteria in the enclosed southern part of Vembanadu Lake may be resulting from the altered flow patterns due to the salt water regulator.

An isentropic flow algorithm with body fitted meshes

An efficient algorithm based on flux difference splitting is presented for the solution of the three-dimensional equations of isentropic flow in a generalised coordinate system, and with a general convex gas law. The scheme is based on solving linearised Riemann problems approximately and in more than one dimension incorporates operator splitting. The algorithm requires only one function evaluation of the gas law in each computational cell. The scheme has good shock capturing properties and the advantage of using body-fitted meshes. Numerical results are shown for Mach 3 flow of air past a circular cylinder. Furthermore, the algorithm also applies to shallow water flows by employing the familiar gas dynamics analogy.

Catchment phosphorous losses: an export coefficient modelling approach with scenario analysis for water management

This paper presents the development of an export coefficient model to characterise the rates and sources of P export from land to water in four reservoir systems located in a semi-arid rural region in southern of Portugal. The model was developed to enable effective management of these important water resource systems under the EU Water Framework Directive. This is the first time such an approach has been fully adapted for the semi-arid systems typical of Mediterranean Europe. The sources of P loading delivered to each reservoir from its catchment were determined and scenario analysis was undertaken to predict the likely impact of catchment management strategies on the scale of rate of P loading delivered to each water body from its catchment. The results indicate the importance of farming and sewage treatment works/collective septic tanks discharges as the main contributors to the total diffuse and point source P loading delivered to the reservoirs, respectively. A reduction in the total P loading for all study areas would require control of farming practices and more efficient removal of P from human wastes prior to discharge to surface waters. The scenario analysis indicates a strategy based solely on reducing the agricultural P surplus may result in only a slow improvement in water quality, which would be unlikely to support the generation of good ecological status in reservoirs. The model application indicates that a reduction of P-inputs to the reservoirs should first focus on reducing P loading from sewage effluent discharges through the introduction of tertiary treatment (P-stripping) in all major residential areas. The fully calibrated export coefficient modelling approach transferred well to semi-arid regions, with the only significant limitation being the availability of suitable input data to drive the model. Further studies using this approach in semi-arid catchments are now needed to increase the knowledge of nutrient export behaviours in semi-arid regions.

The determination of total nitrogen and total phosphorus concentrations in freshwaters from land use, stock headage and population data: testing of a model for use in conservation and water quality management

1. Nutrient concentrations (particularly N and P) determine the extent to which water bodies are or may become eutrophic. Direct determination of nutrient content on a wide scale is labour intensive but the main sources of N and P are well known. This paper describes and tests an export coefficient model for prediction of total N and total P from: (i) land use, stock headage and human population; (ii) the export rates of N and P from these sources; and (iii) the river discharge. Such a model might be used to forecast the effects of changes in land use in the future and to hindcast past water quality to establish comparative or baseline states for the monitoring of change. 2. The model has been calibrated against observed data for 1988 and validated against sets of observed data for a sequence of earlier years in ten British catchments varying from uplands through rolling, fertile lowlands to the flat topography of East Anglia. 3. The model predicted total N and total P concentrations with high precision (95% of the variance in observed data explained). It has been used in two forms: the first on a specific catchment basis; the second for a larger natural region which contains the catchment with the assumption that all catchments within that region will be similar. Both models gave similar results with little loss of precision in the latter case. This implies that it will be possible to describe the overall pattern of nutrient export in the UK with only a fraction of the effort needed to carry out the calculations for each individual water body. 4. Comparison between land use, stock headage, population numbers and nutrient export for the ten catchments in the pre-war year of 1931, and for 1970 and 1988 show that there has been a substantial loss of rough grazing to fertilized temporary and permanent grasslands, an increase in the hectarage devoted to arable, consistent increases in the stocking of cattle and sheep and a marked movement of humans to these rural catchments. 5. All of these trends have increased the flows of nutrients with more than a doubling of both total N and total P loads during the period. On average in these rural catchments, stock wastes have been the greatest contributors to both N and P exports, with cultivation the next most important source of N and people of P. Ratios of N to P were high in 1931 and remain little changed so that, in these catchments, phosphorus continues to be the nutrient most likely to control algal crops in standing waters supplied by the rivers studied.

The effect of a new drag-law parameterization on ice shelf water plume dynamics

A drag law accounting for Ekman rotation adjacent to a flat, horizontal bou ndary is proposed for use in a plume model that is written in terms of the depth-mean velocity. The drag l aw contains a variable turning angle between the mean velocity and the drag imposed by the turbulent bound ary layer. The effect of the variable turning angle in the drag law is studied for a plume of ice shelf wat er (ISW) ascending and turning beneath an Antarctic ice shelf with draft decreasing away from the groundi ng line. As the ISW plume ascends the sloping ice shelf–ocean boundary, it can melt the ice shelf, wh ich alters the buoyancy forcing driving the plume motion. Under these conditions, the typical turning ang le is of order 10° over most of the plume area for a range of drag coefficients (the minus sign arises for th e Southern Hemisphere). The rotation of the drag with respect to the mean velocity is found to be signifi cant if the drag coefficient exceeds 0.003; in this case the plume body propagates farther along and across the b ase of the ice shelf than a plume with the standard quadratic drag law with no turning angle.

The implications of climate change for the water environment in England

This paper reviews the implications of climate change for the water environment and its management in England. There is a large literature, but most studies have looked at flow volumes or nutrients and none have considered explicitly the implications of climate change for the delivery of water management objectives. Studies have been undertaken in a small number of locations. Studies have used observations from the past to infer future changes, and have used numerical simulation models with climate change scenarios. The literature indicates that climate change poses risks to the delivery of water management objectives, but that these risks depend on local catchment and water body conditions. Climate change affects the status of water bodies, and it affects the effectiveness of measures to manage the water environment and meet policy objectives. The future impact of climate change on the water environment and its management is uncertain. Impacts are dependent on changes in the duration of dry spells and frequency of ‘flushing’ events, which are highly uncertain and not included in current climate scenarios. There is a good qualitative understanding of ways in which systems may change, but interactions between components of the water environment are poorly understood. Predictive models are only available for some components, and model parametric and structural uncertainty has not been evaluated. The impacts of climate change depend on other pressures on the water environment in a catchment, and also on the management interventions that are undertaken to achieve water management objectives. The paper has also developed a series of consistent conceptual models describing the implications of climate change for pressures on the water environment, based around the source-pathway-receptor concept. They provide a framework for a systematic assessment across catchments and pressures of the implications of climate change for the water environment and its management.

Using high-frequency water quality data to assess sampling strategies for the EU Water Framework Directive

The EU Water Framework Directive (WFD) requires that the ecological and chemical status of water bodies in Europe should be assessed, and action taken where possible to ensure that at least "good" quality is attained in each case by 2015. This paper is concerned with the accuracy and precision with which chemical status in rivers can be measured given certain sampling strategies, and how this can be improved. High-frequency (hourly) chemical data from four rivers in southern England were subsampled to simulate different sampling strategies for four parameters used for WFD classification: dissolved phosphorus, dissolved oxygen, pH and water temperature. These data sub-sets were then used to calculate the WFD classification for each site. Monthly sampling was less precise than weekly sampling, but the effect on WFD classification depended on the closeness of the range of concentrations to the class boundaries. In some cases, monthly sampling for a year could result in the same water body being assigned to three or four of the WFD classes with 95% confidence, due to random sampling effects, whereas with weekly sampling this was one or two classes for the same cases. In the most extreme case, the same water body could have been assigned to any of the five WFD quality classes. Weekly sampling considerably reduces the uncertainties compared to monthly sampling. The width of the weekly sampled confidence intervals was about 33% that of the monthly for P species and pH, about 50% for dissolved oxygen, and about 67% for water temperature. For water temperature, which is assessed as the 98th percentile in the UK, monthly sampling biases the mean downwards by about 1 °C compared to the true value, due to problems of assessing high percentiles with limited data. Low-frequency measurements will generally be unsuitable for assessing standards expressed as high percentiles. Confining sampling to the working week compared to all 7 days made little difference, but a modest improvement in precision could be obtained by sampling at the same time of day within a 3 h time window, and this is recommended. For parameters with a strong diel variation, such as dissolved oxygen, the value obtained, and thus possibly the WFD classification, can depend markedly on when in the cycle the sample was taken. Specifying this in the sampling regime would be a straightforward way to improve precision, but there needs to be agreement about how best to characterise risk in different types of river. These results suggest that in some cases it will be difficult to assign accurate WFD chemical classes or to detect likely trends using current sampling regimes, even for these largely groundwater-fed rivers. A more critical approach to sampling is needed to ensure that management actions are appropriate and supported by data.

Drinking water application of Denargard Tiamulin for control of Brachyspira pilosicoli infection of laying poultry

Avian intestinal spirochaetosis (AIS) caused by Brachyspira spp., and notably Brachyspira pilosicoli, is common in layer flocks and reportedly of increasing incidence in broilers and broiler breeders. Disease manifests as diar- rhoea, increased feed consumption, reduced growth rates and occasional mortality in broilers and these signs are shown in layers also associated with a delayed onset of lay, reduced egg weights, faecal staining of eggshells and non-productive ovaries. Treatment with Denagard® Tiamulin has been used to protect against B. pilosicoli colonisation, persistence and clinical presentation of AIS in commercial layers, but to date there has been no de- finitive study validating efficacy. Here, we used a poultry model of B. pilosicoli infection of layers to compare the impact of three doses of Denagard® Tiamulin. Four groups of thirty 17 week old commercial pre-lay birds were all challenged with B. pilosicoli strain B2904 with three oral doses two days apart. All birds were colonised within 2 days after the final oral challenge and mild onset of clinical signs were observed thereafter. A fifth group that was unchallenged and untreated was also included for comparison as healthy birds. Five days after the final oral Brachypira challenge three groups were given Denagard® Tiamulin in drinking water made up following the manufacturer's recommendations with doses verified as 58.7 ppm, 113 ppm and 225 ppm. Weight gain body condition and the level of diarrhoea of birds infected with B. pilosicoli were improved and shedding of the organism reduced significantly (p = 0.001) following treatment with Denagard® Tiamulin irrespective of dose given. The level and duration of colonisation of organs of birds infected with B. pilosicoli was also reduced. Confirming previous findings we showed that the ileum, caeca, colon, and both liver and spleen were colonised and here we demonstrated that treatment with Denagard® Tiamulin resulted in significant reduction in the numbers of Brachyspira found in each of these sites and dramatic reduction in faecal shedding (p b 0.001) to ap- proaching zero as assessed by culture of cloacal swabs. Although the number of eggs produced per bird and the level of eggshell staining appeared unaffected, egg weights of treated birds were greater than those of untreated birds for a period of approximately two weeks following treatment. These data conclusively demonstrate the ef- fectiveness of Denagard® Tiamulin in reducing B. pilosicoli infection in laying hens.

Drinking water application of Denagard® Tiamulin for control of Brachyspira pilosicoli infection of laying poultry

Avian intestinal spirochaetosis (AIS) caused by Brachyspira spp., and notably Brachyspira pilosicoli, is common in layer flocks and reportedly of increasing incidence in broilers and broiler breeders. Disease manifests as diarrhoea,increased feed consumption, reduced growth rates and occasional mortality in broilers and these signs are shown in layers also associated with a delayed onset of lay, reduced egg weights, faecal staining of eggshells and non-productive ovaries. Treatment with Denagard® Tiamulin has been used to protect against B. pilosicoli colonisation, persistence and clinical presentation of AIS in commercial layers, but to date there has been no definitive study validating efficacy. Here, we used a poultry model of B. pilosicoli infection of layers to compare the impact of three doses of Denagard® Tiamulin. Four groups of thirty 17 week old commercial pre-lay birds were all challengedwith B. pilosicoli strain B2904with three oral doses two days apart. All birdswere colonised within 2 days after the final oral challenge and mild onset of clinical signs were observed thereafter. A fifth group that was unchallenged and untreated was also included for comparison as healthy birds. Five days after the final oral Brachypira challenge three groups were given Denagard® Tiamulin in drinking water made up following the manufacturer's recommendations with doses verified as 58.7 ppm, 113 ppm and 225 ppm. Weight gain body condition and the level of diarrhoea of birds infected with B. pilosicoli were improved and shedding of the organism reduced significantly (p = 0.001) following treatment with Denagard® Tiamulin irrespective of dose given. The level and duration of colonisation of organs of birds infected with B. pilosicoli was also reduced. Confirming previous findings we showed that the ileum, caeca, colon, and both liver and spleen were colonised and here we demonstrated that treatment with Denagard® Tiamulin resulted in significant reduction in the numbers of Brachyspira found in each of these sites and dramatic reduction in faecal shedding (p b 0.001) to approaching zero as assessed by culture of cloacal swabs. Although the number of eggs produced per bird and the level of eggshell staining appeared unaffected, egg weights of treated birds were greater than those of untreated birds for a period of approximately two weeks following treatment. These data conclusively demonstrate the effectiveness of Denagard® Tiamulin in reducing B. pilosicoli infection in laying hens.