Water Intake In Rats Research Articles

Evaluation of water intake rate using the diffusive tank model in the low-lying paddy area

The subject of this study is water management in low-lying paddy fields. The objective of this study is to quantify the water requirement, and estimate an appropriate volume and facilitate management of irrigation water in areas where it is difficult to estimate the flow rate continuously. A field observation was conducted at a 14-ha study site located in the Kuwabara area, Fukuoka City, southwest of Japan, to evaluate water management conditions in the command area of the reservoir. This site near the reservoir was selected, because it was impossible to understand the water supply situation in the entire command area. The farmers in this region have been unable to retain sufficient irrigation water. The observation results indicate that the water depth fluctuates widely in every irrigation canal. The canals are frequently empty because rotational irrigation is conducted by water managers; this makes quantifying the flow rate in the irrigation canal very difficult. To quantify the water requirement, an improved tank model was introduced. The accuracy of the model was examined by comparing the observed and calculated ponding depths at a paddy field. The simulation results agreed with the observed data. Using this model, water management for the reduction of water managers’ labor was simulated. Simulation results indicated that rotational irrigation effectively reduces labor and saves irrigation water.

Effect of shearing on water turnover and thermobiological variables in German Blackhead mutton sheep1

Current equations for estimating water requirements in sheep do not differentiate between shorn and unshorn sheep. Furthermore, the effect of shearing on thermoregulative responses in sheep has not been adequately studied under temperate environmental conditions. Therefore, the present study was conducted to investigate the effect of wool coverage on water turnover in relation to thermoregulation in sheep by using the deuterium dilution technique to predict total water intake before and after shearing. Physiological responses, such as water turnover, surface temperature, and rectal temperature, as well as drinking behavior of sheep were also evaluated. Fourteen nonlactating German Blackhead mutton ewes were randomly allocated into 2 groups: a control group (n = 7) that was already shorn, and a treatment group (n = 7) that was left unshorn (wool length: 10.6 ± 1.2 cm). Individual feed and water intakes were recorded throughout the experiment (d 1 to 71). Two weeks after measurements commenced (d 15), treatment sheep were shorn. Water intake was estimated twice for 2 consecutive weeks by using deuterium dilution techniques (d 1 to 15 and d 57 to 71). Ambient temperature (T(a)), relative humidity, and respiratory rate were measured daily, whereas BW, rectal and animal surface temperatures (using infrared thermography), and wool length were measured weekly. In the first 2 wk, when treatment sheep were unshorn, treatment and control ewes differed (P < 0.05) in DMI (52 ± 4 vs. 59 ± 4 g·kg(-0.75)·d(-1)), water intake (165 ± 17 vs. 134 ± 18 g·kg(-0.75)·d(-1)), respiratory rate (66 ± 5 vs. 31 ± 4 breath/min), rectal temperature (39.3 ± 0.2 vs. 38.8 ± 0.1°C), and surface temperatures (body side: 19.3 ± 0.3 vs. 24.5 ± 0.6°C; leg: 25.8 ± 2.4 vs. 27.4 ± 1.6°C). However, after shearing, these differences partly disappeared. The same trend in water intake between groups was confirmed using the isotope dilution technique. We found a significant relationship between T(a) and water intake, respiratory rate, and body surface temperatures. Even under temperate conditions (T(a) < 28°C), shearing significantly reduced core body temperature, water intake, and respiratory rate in German Blackhead mutton sheep, thus indicating heat stress in fleeced animals, which should be considered when determining the optimal shearing time in sheep as well as when estimating water requirements.

Role of superior laryngeal nerve and Fos staining following dehydration and rehydration in the rat

Immunohistochemistry for Fos was used to determine the role of the superior laryngeal nerve in conscious rats following water deprivation and rehydration. Adult male rats were subjected to either unilateral superior laryngeal nerve section (SLNX) or sham surgery. Two weeks later rats from each surgical group were water deprived for 48h or water deprived for 46h and given access to water for 2h prior to perfusion. Controls were allowed ad libitum access to water. Brains were processed for Fos using a commercially available antibody. Changes in plasma osmolality and hematocrit were not significantly different between SLNX and sham following any of the treatments. Water intake in rats was not significantly affected by SLNX. In the supraoptic nucleus (SON) of sham rats, water deprivation significantly increased Fos staining while water intake following dehydration prevented this increase. Water deprivation significantly increased Fos staining in the SON of SLNX rats. Following water intake after 46h water deprivation in SLNX rats, Fos staining in the ipsilateral SON was significantly greater than the contralateral SON and significantly lower than 48h water deprivation. In the nucleus of the solitary tract (NTS) of sham rats, both water deprivation and water intake produced significant increases in Fos staining bilaterally compared to euhydrated controls. In SLNX rats, water deprivation significantly increased Fos in both ipsilateral and contralateral NTS that was not different from sham rats. SLNX significantly decreased Fos staining in the ipsilateral NTS of rats given access to water after dehydration compared to the corresponding sham treated rats. Fos staining was not affected in the contralateral NTS of SLNX rats given access to water after dehydration. This suggests that the superior laryngeal nerve contributes to changes in Fos staining in the NTS and SON following water intake in dehydrated rats.

Effects of chromium piclonate and ascorbic acid supplementation on growth performance, carcass traits, blood constituents and picture of growing kids under the summer conditions

The present work was performed to study the effect of chromium piclonate and ⁄ or ascorbic acid supplementation on the performance of growing kids during hot summer season (33.6oC and 74.2% RH). A total number of twenty four weaned commercial kids were randomly distributed into four treatment groups of 6 kids per each Kids in all treatments were equal in number and had nearly similar initial body weight. The first group was fed the basal diet and served as control (0.0 supplementation), while the other three groups were fed diets supplemented with 75 mg/kg diet chromium piclonate, 800 mg/ kg diet ascorbic acid and 75 mg / kg diet chromium piclonate + 800 mg ascorbic acid, respectively. The results obtained for growing Kids showed that the final live body weight and daily body gain were increased significantly (P < 0.05 or 0.01) during 210 and 270 daysfor Kids fed diets supplemented with chromium piclonate, ascorbic acid and chromium piclonate + ascorbic acid. However, the supplementation of chromium piclonate + ascorbic acid seemed to be the best significant performance. The results obtained for growing Kids showed that the daily feed intake, feed conversion, water ⁄ feed intake ratio, water ⁄ daily gain ratio were increased significantly (P < 0.05 or 0.01) during the experimental periods for Kids fed diets supplemented with chromium piclonate, ascorbic acid and chromium piclonate + ascorbic acid. The Results showed that water intake, rectum temperature and respiration rate were not significantly affected by previous treatments. The best margin was obtained in group fed on the diet supplemented with chromium piclonate + ascorbic acid. All carcass traits were increased insignificantly due to dietary chromium piclonate and ⁄or ascorbic acid supplementation. Serum total proteins were increased significantly (P < 0.05), in group three only while the cholesterol level and triglycerides decreased significantly (P<0.05) in Kids treated with chromium piclonate as compared with the control group under summer heat stress conditions. Serum albumin, globulin, urea-, creatinine, AST, WBCs, RBCs MCV, MCH and Hb content were insignificantly affected by chromium piclonate and ⁄or ascorbic acid supplementation to the kids’ diets. Finally, it could be concluded that supplementation of 75 mg chromium piclonate + 800 mg ascorbic acid / kg diet to the kid diets is necessary to improve the productivity, under the summer conditions

Acute and sub-chronic toxicity study of standardized extract of Fumaria indica in rodents

Despite Fumaria indica (FI) widespread medicinal uses in the Indian traditional medicine, no systematic study of the potential toxicity of the plant has been described. To assess acute and sub-chronic toxicity of a 50% ethanolic extract of FI in mice and rats respectively. In acute toxicity study, Swiss strain albino mice of either sex were administered orally FI doses of 1, 2.5 and 5 g/kg and observed for behavioural changes and mortality, if any. In sub-chronic toxicity study, Charles Foster albino rats of either sex were administered two doses of FI i.e., 100 and 400mg/kg, p.o. for 30 consecutive days. During 30 days of treatment, rats were observed for any change in body weight and daily food and water intake. After 30 days, rats were sacrificed for haematological, biochemical and histopathology study. Control animals were administered 0.3% carboxymethyl cellulose (CMC) suspension by oral route. There was no mortality or abnormal behaviour, observed in acute toxicity study in mice at all the three dose levels. In sub-chronic toxicity study, FI did not produce any significant change in body weight and daily food and water intake of rats when compared to vehicle treated rats. Further, haematological and biochemical parameters were also found normal. Histopathological study revealed normal architecture of kidney and liver of FI treated rats. FI extract, provisionally standardized on its fumarate contents, seems to fulfill a preclinical criterion necessary for its further development as a clinically useful adaptogen.

Arsenic Exposure from Rice and Water Sources in the Noakhali District of Bangladesh

Drinking water and food are the two major routes of the consumption of arsenic (As) by people in Bangladesh. This study reports exposure of adults in two adjacent rural villages of Bangladesh to As from drinking water and rice. Uncooked and cooked rice, drinking and cooking water, were sampled from 14 families to determine total As concentrations. Arsenic speciation in uncooked rice was also conducted to determine the percentage of inorganic As (arsenite and arsenate). Arsenic intake by people from rice and drinking water was also assessed. The average water intake rates were 3.2 and 2.7 L per day for adult males and females, respectively, whereas no significant gender difference was observed for rice intake. The study revealed that with one exception, all the families examined drank As-contaminated groundwater. They used As-safe pond water for cooking. The mean As concentrations in drinking and cooking water were 328 and 2.5 μg/L, respectively. The average As concentrations in uncooked and cooked rice were 153 and 139 μg/kg (dry weight), respectively. On average, 73% of the As present in uncooked rice was inorganic. The study showed that adult males and females consume 1099 and 933 μg of inorganic As per day, respectively, from rice consumption and drinking water. Rice contributed 49 and 47 μg per day of inorganic As for adult males and females, respectively. The study concluded that the villagers in the study area consumed considerable amount of As from drinking water and that exposure from rice was also not negligible, despite intensive programs by governmental and non-governmental agencies to reduce villagers’ exposure to As consumption.

INTERACTION OF INTRACEREBROVENTRICULAR INJECTION OF CAPTOPRIL AND HISTAMINE ON WATER INTAKE IN ADULT MALE WISTAR RATS

Several evidences have indicated that many nuclei in the brain have critical role in water intake. Angiotensin II is one of the most important neurotransmitters involved in regulation of fluid homeostasis. In this study, the interaction of i.c.v. injection of captopril and histamine on water intake in adult male water-deprived rats was investigated. Rats were implanted with guide cannula aimed toward lateral ventericle. After recovery period, the animals deprived of water for 24 h, and then, drugs were injected and the volume of water intake was measured for 1 hour. The results showed that captopril (7 and 10 µg/rat) decreased, while histamine (40 and 80 µg/rat) increased the rate of water intake. Meanwhile, captopril pretreatment blocked the responses induced by histamine. These data suggest that histamine and angiotensin systems may have an interaction on water intake mechanism.

Synthesis, Characterization, and Drying of Absorbable Gelatin Foam

This research article pertains to a process for the preparation of lyophilized absorbable gelatin sponge. The Kenics static mixer was used for gelatin foam preparation and subsequently lyophilized in a freeze dryer. The lyophilized sponge was characterized for its pore size, bulk density, degree of cross-linking, mechanical stability, water absorption capacity, water intake rate, and thermal stability. The extent of cross-linking was evaluated by gelatin solubility test method. With increasing concentration of formaldehyde, Young's modulus and the stress at break increases and the strain at break decreases. Simultaneously, cross-linking provokes a significant reduction of swelling in water and it enhances the thermal stability of the sample as indicated by the differential scanning calorimetry (DSC) investigations. The pore size and bulk density of the dried sponge was found to increase from 100 to 500 µm and decrease from 26.7 to 22.4 kg/m3, respectively, with an increase in freezing temperature from −70 to −20°C. The drying study at different temperatures reveals that the effective diffusivity of moisture in foam increases from 7.5396 × 10−8 to 9.8285 × 10−8 m2/s with an increase in drying temperature from 40 to 60°C during the desorption stage. The sponge prepared from gelatin can be utilized as a promising matrix for wound healing and other surgical applications.

Role of nitric oxide in hypodipsia of rats with obstructive cholestasis.

Cholestasis is associated with the overproduction of nitric oxide (NO), and NO acts as an inhibitory mechanism when thirst is stimulated by water deprivation or by angiotensin II. Due to the presence of hypodipsia in the cholestatic condition, we have compared the rate of water intake between bile duct-ligated (cholestatic) and sham-operated rats. We have evaluated the effect of NO synthesis inhibition by N(G)-nitro-L-arginine (L-NNA, 10 mg kg(-1)/day) on the rate of water intake in cholestatic rats. The results showed that plasma alkaline phosphatase activity (a marker of liver damage) increased after bile-duct ligation, and that its elevation was partially (but significantly) prevented by treatment with L-arginine. A two-week bile-duct obstruction induced a significant decrease in the rate of water intake compared with sham-operated animals (35.87 +/- 1.45 vs 42.37 +/- 1.99 mL/day, P < 0.05). This effect was corrected by the daily administration of L-NNA. Surprisingly, L-arginine (200 mg kg(-1)/day) showed similar activity as L-NNA in cholestatic rats and increased water intake, but not in control animals. Systemic NO synthesis inhibition corrected the decrease in water intake observed in cholestatic rats. This suggests an important role for NO in the pathophysiology of hypodipsia in cholestatic subjects. The effect of chronic L-arginine administration observed in cholestatic rats but not seen in the control rats could be explained theoretically by the amelioration of cholestasis-induced liver damage by chronic L-arginine administration in bile duct-ligated rats.

Microinjection of NMDA Receptor Agents into the Central Nucleus of the Amygdale Alters Water Intake in Rats

The central nucleus of the amygdala (CeA) is a forebrain structure which is important in regulation of ingestive behavior and there is direct and circumstantial evidence to indicate that some circuits involved with feeding behavior include glutamatergic elements. The present study examined whether administration of NMA (N-Methyl-DL-aspartic acid) or MK801 into the CeA altered water intake under deprivation. Materials and Methods Animals were deprived for 24 hr before tested for water intake. NMDA (N-methyl-D-aspartate) glutamatergic receptor agonist, NMA and its antagonist, MK801 were infused bilaterally, and water intake measured for 1 hr thereafter. Results The intra-CeA injection of NMDA glutamatergic agonist, NMA (0.25, 0.5 and 0.75 µg/rat) increased water intake (P<0.05). However, administration of NMDA glutamatergic antagonist, MK801 (0.25, 0.5 and 1 µg/rat) decreased water intake significantly (P<0.05). Conclusion These data suggest that NMDA receptors in the CeA are responsible for the glutamatergic modulation of water intake in this nucleus.

Water intake rate among the general Korean population

Public concerns about water pollution have led to the assessment of risks associated with waterborne pollutants. The water intake rate is a key exposure factor that needs to be employed in the risk assessment of water contaminants. However, water consumption patterns vary considerably due to many factors, including region, culture, and time. Because limited information is available on the water intake rate in Asian countries, we carried out a nationwide survey using an online questionnaire to assess the direct tap water and beverage consumption within the general Korean population. To measure seasonal variation in water consumption, this survey was conducted twice, in the spring ( n = 1092) and summer ( n = 1148) of 2006. Water intake rates were assessed by age, gender, season, and region. The average rate total water intake was 2566.2 ml/day (direct tap water 1015.9 ml/day; beverage 1073.0 ml/day; indirect tap water 477.3 ml/day) in the spring. Indirect tap water intake through the consumption of water-rich dishes occupies 18.5% of average total water intake. In the summer, the average consumption of direct tap water and beverages increased by up to 19.7 and 7.6%, respectively. For the exposure assessment of water related environmental contaminants, a value of 1493 mg/L is proposed as a central tendency value and for a reasonable maximum, a value of 2914 mg/L (90th percentile) is suggested. This exposure factor may be used in regions with geographic and ethnic characteristics similar to Korea.

An Assessment of Potential Exposure and Risk from Estrogens in Drinking Water

BackgroundDetection of estrogens in the environment has raised concerns in recent years because of their potential to affect both wildlife and humans.ObjectivesWe compared exposures to prescribed and naturally occurring estrogens in drinking water to exposures to naturally occurring background levels of estrogens in the diet of children and adults and to four independently derived acceptable daily intakes (ADIs) to determine whether drinking water intakes are larger or smaller than dietary intake or ADIs.MethodsWe used the Pharmaceutical Assessment and Transport Evaluation (PhATE) model to predict concentrations of estrogens potentially present in drinking water. Predicted drinking water concentrations were combined with default water intake rates to estimate drinking water exposures. Predicted drinking water intakes were compared to dietary intakes and also to ADIs. We present comparisons for individual estrogens as well as combined estrogens.ResultsIn the analysis we estimated that a child’s exposures to individual prescribed estrogens in drinking water are 730–480,000 times lower (depending upon estrogen type) than exposure to background levels of naturally occurring estrogens in milk. A child’s exposure to total estrogens in drinking water (prescribed and naturally occurring) is about 150 times lower than exposure from milk. Adult margins of exposure (MOEs) based on total dietary exposure are about 2 times smaller than those for children. Margins of safety (MOSs) for an adult’s exposure to total prescribed estrogens in drinking water vary from about 135 to > 17,000, depending on ADI. MOSs for exposure to total estrogens in drinking water are about 2 times lower than MOSs for prescribed estrogens. Depending on the ADI that is used, MOSs for young children range from 28 to 5,120 for total estrogens (including both prescribed and naturally occurring sources) in drinking water.ConclusionsThe consistently large MOEs and MOSs strongly suggest that prescribed and total estrogens that may potentially be present in drinking water in the United States are not causing adverse effects in U.S. residents, including sensitive subpopulations.

Assessing Children's Exposures and Risks to Drinking Water Contaminants: A Manganese Case Study

ABSTRACT Background: Compared to adults, children maybe more highly exposed to toxic substances in drinking water because they consume more water per unit of body weight. The U.S. Environmental Protection Agency (USEPA) has developed new guidance for selecting age groups and age-specific exposure factors for assessing children's exposures and risks to environmental contaminants. Research Aim: To demonstrate the application and importance of applying age-specific drinking water intake rates, health reference values, and exposure scenarios when assessing drinking water exposures because these approaches illustrate the potential for greater potential for adverse health effects among children. Methods: manganese, an essential nutrient and neurotoxicant, was selected as a case study and chemical of potential concern for children's health. A screening-level risk assessment was performed using age-specific drinking water intake rates and manganese concentrations from U.S. public drinking water systems. Results: When age-specific drinking water intake rates are used to calculate dose, formula-fed infants receive the highest dose of manganese from drinking water compared to all other age groups. Estimated hazard quotients suggest adverse health effects are possible. Use of USEPA's standardized childhood age groups and childhood exposure factors significantly improves the understanding of childhood exposure and risks.

Centrally administered ghrelin potently inhibits water intake induced by angiotensin II and hypovolemia in rats

Ghrelin is a potent, centrally acting orexigenic hormone. Recently, we showed that centrally administered ghrelin is a potent antidipsogenic hormone in 24-h water deprived rats. In this study, we examined the effect of intracerebroventricular (icv) injection of ghrelin on angiotensin II (AII)-induced water intake in rats. We also examined the effects of icv injection of ghrelin on drinking induced by intraperitoneal injection of an isotonic polyethylene glycol (PEG) solution that causes isotonic hypovolemia. Water intake induced by the icv injection of AII or ip injection of PEG was significantly reduced after icv injection of ghrelin, although food intake was stimulated by the hormone. The drinking induced by AII was also inhibited by the icv administration of 4alpha-phorbol 12, 13-didecanoate, an agonist of the osmosensitive TRPV4 channel. This study showed that ghrelin is a potent antidipsogenic peptide by antagonizing general dipsogenic mechanisms including those activated by AII and hypovolemia in rats.

Development of health-based drinking water guidance for PFOA

Perfluorooctanoic acid (PFOA) is a synthetic, perfluorinated organic acid previously used in fluoropolymer production in the United States. PFOA has been a recent focal point for regulation because of its ubiquitous presence in drinking water throughout the United States. In 2016, the United States Environmental Protection Agency (US EPA) issued a lifetime drinking water Health Advisory (HA) for PFOA of 0.07 μg/L; several states have also implemented their own drinking water guidelines for PFOA. The current study aimed to evaluate the basis and derivation of state and federal guidelines for PFOA in drinking water, with particular emphasis on the exposure parameters utilized. Twelve distinct PFOA drinking water standards were identified ranging from 0.0051 to 2 μg/L. The US EPA HA assumptions were evaluated using a Monte Carlo analysis that included distributions for drinking water intake (DWI) rate and the relative source contribution (RSC). We determined that US EPA's HA of 0.07 μg/L is protective of 99% of the population of lactating women. We also demonstrated that the health-based guidelines were highly variable across states and that the actual RSC of PFOA from drinking water is likely greater than 20%, based on studies of actual PFOA exposures from dust, water, and food. A sensitivity analysis was performed using the same equations as the US EPA, while substituting the RSC and DWI variables; resulting in HAs ranging from 0.074 to 0.346 μg/L. We also evaluated the contribution of PFOA in drinking water to the systemic PFOA body burden of the general population using an available biokinetic model. We conclude that more rigorous efforts are warranted to establish consistent health-based drinking water guidelines for PFOA, given that drinking water is a primary source of human exposure to PFOA in the United States.

Diminished Metabolic Responses to Centrally‐Administered Apelin‐13 in Diet‐Induced Obese Rats Fed a High‐Fat Diet

The central administration of apelin, a recently identified adipokine, has been shown to affect food and water intake. The present study investigated whether body weight could affect an animal's response to apelin. The effects of centrally-administered apelin-13 on food and water intake, activity and metabolic rate were investigated in adult male diet-induced obese (DIO) rats fed either a high fat (32%) or control diet. Rats were administered i.c.v. apelin-13, 15-30 min prior to lights out, and food and water intake, activity and metabolic rate were assessed. Intracerebroventricular administration of apelin-13 decreased food and water intake and respiratory exchange ratio in DIO rats on the control diet, but had no effect in DIO rats on the high-fat diet. In an effort to identify potential central mechanisms explaining the observed physiological responses, the mRNA level of the apelin receptor, APJ, was examined in the hypothalamus. A high-fat diet induced an up-regulation of the expression of the receptor. Apelin induced a down-regulation of the receptor, but only in the DIO animals on the high-fat diet. In conclusion, we have demonstrated a diminished central nervous system response to apelin that is coincident with obesity.

Radium and 40K in Algerian bottled mineral waters and consequent doses

Concentrations of (226)Ra, (228)Ra and (40)K in the five most popular Algerian bottled mineral waters have been found to be 13.9 to 148.9 mBq l(-1), 7.2 to 52.9 mBq l(-1) and <0.07 to 2.19 Bq l(-1), respectively. Ratios of (226)Ra to (228)Ra activities ranged from 1.0 to 13.66 with a mean of 5.62. The annual effective doses due to ingestion of these waters have been estimated for three age categories (infants, children and adults) using the measured activities of these radionuclides and assuming the World Health Organisation's default water intake rate. Annual doses for children and adults have been found to be well below the 0.1 mSv y(-1) reference dose level, whereas for the most vulnerable group the annual effective dose from all the waters exceeds the reference value and contributes 12% to the mean annual dose from natural exposure.

Effects of sodium chloride and fat supplementation on finishing steers exposed to hot and cold conditions

Three studies were conducted to evaluate the effects of supplemental fat and salt (sodium chloride) on DMI, daily water intake (DWI), body temperature, and respiration rate (RR) in Bos taurus beef cattle. In Exp. 1 and 2, whole soybeans (SB) were used as the supplemental fat source. In Exp. 3, palm kernel meal and tallow were used. Experiment 1 (winter) and Exp. 2 (summer) were undertaken in an outside feedlot. Experiment 3 was conducted in a climate-controlled facility (mean ambient temperature = 29.9 degrees C). In Exp. 1, three diets, 1) control; 2) salt (control + 1% sodium chloride); and 3) salt-SB (control + 5% SB + 1% sodium chloride), were fed to 144 cattle (BW = 327.7 kg), using a replicated 3 x 3 Latin square design. In Exp. 2, 168 steers (BW = 334.1 kg) were used. In Exp. 2, the same dietary treatments were used as in Exp. 1, and a 5% SB dietary treatment was included in an incomplete 3 x 4 Latin square design. In Exp. 3, three diets, 1) control; 2) salt (control + 0.92% NaCl); and 3) salt-fat (control + 3.2% added fat + 0.92% NaCl) were fed to 12 steers (BW = 602 kg) in a replicated Latin square design. In Exp. 1, cattle fed the salt-SB diet had elevated (P < 0.05) tympanic temperature (TT; 38.83 degrees C) compared with cattle fed the control (38.56 degrees C) or salt (38.50 degrees C) diet. In Exp. 2, cattle fed the salt and salt-SB diets had less (P < 0.05) DMI and greater (P < 0.05) DWI than cattle in the control and SB treatments. Cattle fed the salt-SB diet had the greatest (P < 0.05) TT (38.89 degrees C). Those fed only the salt diet or only the SB diet had the least (P < 0.05) TT, at 38.72 and 38.78 degrees C, respectively. Under hot conditions (Exp. 3), DMI of steers fed the salt and salt-fat diets declined by approximately 40% compared with only 24% for the control cattle. During hot conditions, DWI was greatest (P < 0.05) for steers on the salt-fat diet. These steers also had the greatest (P < 0.05) mean rectal temperature (40.03 +/- 0.1 degrees C) and RR (112.7 +/- 1.7 breaths/min). The RR of steers on the control diet was the least (P < 0.05; 98.3 +/- 1.7 breaths/min). Although added salt plus fat decreased DMI under hot conditions, these data suggest that switching to diets containing the combination of added salt and fat can elevate body temperature, which would be a detriment in the summer but a benefit to the animal during winter. Nevertheless, adding salt plus fat to diets resulted in increased DWI under hot conditions. Diet ingredients or the combination of ingredients that can be used to regulate DMI may be useful to limit large increases in DMI during adverse weather events.

A nectar-feeding mammal avoids body fluid disturbances by varying renal function

To maintain water and electrolyte balance, nectar-feeding vertebrates oscillate between two extremes: avoiding overhydration when feeding and preventing dehydration during fasts. Several studies have examined how birds resolve this osmoregulatory dilemma, but no data are available for nectar-feeding mammals. In this article, we 1) estimated the ability of Pallas's long-tongued bats (Glossophaga soricina; Phyllostomidae) to dilute and concentrate urine and 2) examined how water intake affected the processes that these bats use to maintain water balance. Total urine osmolality in water- and salt-loaded bats ranged between 31 +/- 37 mosmol/kgH(2)O (n = 6) and 578 +/- 56 mosmol/kgH(2)O (n = 2), respectively. Fractional water absorption in the gastrointestinal tract was not affected by water intake rate. As a result, water flux, body water turnover, and renal water load all increased with increasing water intake. Despite these relationships, glomerular filtration rate (GFR) was not responsive to water loading. To eliminate excess water, Pallas's long-tongued bats increased water excretion rate by reducing fractional renal water reabsorption. We also found that rates of total evaporative water loss increased with increasing water intake. During their natural daytime fast, mean GFR in Pallas's long-tongued bats was 0.37 ml/h (n = 10). This is approximately 90% lower than the GFR we measured in fed bats. Our findings 1) suggest that Pallas's long-tongued bats do not have an exceptional urine-diluting or -concentrating ability and 2) demonstrate that the bats eliminate excess ingested water by reducing renal water reabsorption and limit urinary water loss during fasting periods by reducing GFR.

Approaches for Evaluating the Relevance of Multiroute Exposures in Establishing Guideline Values for Drinking Water Contaminants

In establishing the guideline values for chemical contaminants in drinking water, the contribution of inhalation and dermal routes associated with showering/bathing needs to be evaluated. The present article reviews the current approaches available for evaluating the importance of inhalation and dermal routes of exposure to drinking water contaminants (DWCs) and integrates them within a 2-tier approach. Accordingly, tier 1 would evaluate whether the dermal or inhalation route is likely to contribute to at least 10% of the dose received from ingestion of drinking water (i.e., 0.15 L-equivalent per day based on the daily water intake rate of 1.5 L/day typically used in Health Canada assessments). Based on the route-specific exposure parameters (i.e., area of skin exposed, effective skin permeability coefficient [Kp], and air to water concentration ratio during use conditions [Fair-water], breathing rate, duration of contact, and fraction absorbed), it was determined that for DWCs with Kp less than 0.024 cm/hr and Fair - water less than 0.0063, the dermal and inhalation routes during showering or bathing are unlikely to contribute significantly to the total dose. For DWCs with Kp value equal to or greater than 0.025 cm/hr, dermal notation is implied, and as such, tier 2 calculation of L-equivalent associated with dermal exposure needs to be performed. Similarly, for DWCs with Fair-water greater than 0.00063, inhalation notation is implied, and detailed evaluation of the L-equivalent associated with inhalation exposure (i.e., tier 2) is suggested. In general, data from human volunteer studies, observational measurements, and targeted modeling studies are useful for deriving L-equivalents, reflective of the magnitude of dose received via dermal and inhalation routes relative to the oral route. However, in resource-limited situations, these approaches can be integrated within a 2-tier approach for prioritizing and providing quantitative evaluations of the relevance of dermal and inhalation routes for developing exposure guidelines for DWCs.