Pilot Study Examining the Influence of Potassium Bicarbonate Supplementation on Nitrogen Balance and Whole-Body Ammonia and Urea Turnover Following Short-Term Energy Restriction in Older Men.

With aging there is a chronic low-grade metabolic-acidosis that may exacerbate negative protein balance during weight loss. The objective of this randomized pilot study was to assess the impact of 90 mmol∙day-1 potassium bicarbonate (KHCO3) versus a placebo (PLA) on 24-h urinary net acid excretion (NAE), nitrogen balance (NBAL), and whole-body ammonia and urea turnover following short-term diet-induced weight loss. Sixteen (KHCO3; n = 8, PLA; n = 8) older (64 ± 4 years) overweight (BMI: 28.5 ± 2.1 kg∙day-1) men completed a 35-day controlled feeding study, with a 7-day weight-maintenance phase followed by a 28-day 30% energy-restriction phase. KHCO3 or PLA supplementation began during energy restriction. NAE, NBAL, and whole-body ammonia and urea turnover (15N-glycine) were measured at the end of the weight-maintenance and energy-restriction phases. Following energy restriction, NAE was -9.8 ± 27.8 mmol∙day-1 in KHCO3 and 43.9 ± 27.8 mmol∙day-1 in PLA (p < 0.05). No significant group or time differences were observed in NBAL or ammonia and urea turnover. Ammonia synthesis and breakdown tended (p = 0.09) to be higher in KHCO3 vs. PLA following energy restriction, and NAE was inversely associated (r = -0.522; p < 0.05) with urea synthesis in all subjects. This pilot study suggests some benefit may exist with KHCO3 supplementation following energy restriction as lower NAE indicated higher urea synthesis.

Metabolomics combined with pattern recognition and bioinformatics analysis methods for the development of pharmacodynamic biomarkers on liver fibrosis.

The major obstacle for the development of targeted therapies is the lack of pharmacodynamic (PD) biomarkers to provide an early readout of biological activities. As the modulation of metabolites may reflect the biological changes occurring in the targets, metabolomics is promising to be an efficient way to explore PD biomarkers. In the present study, a liver fibrosis rat model was established by intraperitoneal injection of CCl4 twice weekly for 6 weeks, the treatment of total aglycone extracts of Scutellaria baicalensis (TAES) was begun 4 weeks after the modeling, and gas chromatography-mass spectrometry (GC-MS) based metabolomics combined with pattern recognition and network analysis were carried out for the research on PD biomarkers of TAES on liver fibrosis. After 2 weeks of treatment, TAES shows positive effects on CCl4-induced liver fibrosis. In the metabolomics study, 63 urinary metabolites contributing to liver fibrosis were identified. Six metabolic pathways significantly enriched in metabolomics data were mapped onto a network to determine global patterns of metabolic alterations in liver fibrosis. By topological analysis, 6 metabolites with high centrality in the metabolic sub-network were selected as potential PD biomarkers. Within 24 h of the final administration, the 6 identified urine metabolic biomarkers with response to time variation of TAES were validated as PD biomarkers. This integrative study presents an attractive strategy to explore PD biomarkers, which may give insight into the actual pharmacological effect of target drugs, and the information from PD biomarkers can be combined with pharmacokinetics to select the optimal dose and a schedule of administration for the drugs.

Determination of the safety of leucine supplementation in healthy elderly men.

Leucine, a branched-chain amino acid (BCAA), has been shown to stimulate muscle protein synthesis, and thus has been proposed to prevent age-related muscle atrophy (sarcopenia). Therefore, leucine supplementation may have potential benefits in elderly populations to preserve muscle mass. The tolerable upper intake level (UL) for leucine intake in young men has recently been determined to be 500 mg kg(-1) day(-1), and increases in blood ammonia concentrations were seen at intake levels above 500 mg kg(-1) day(-1); the UL for leucine in elderly is unknown. The objective of the current study was to determine the safety of leucine supplementation in healthy elderly men. Six healthy elderly men (72.2 ± 3.5 years) received graded stepwise increases in leucine intakes ranging from 50 to 750 mg kg(-1) day(-1), on eight separate study days. Plasma and urinary biochemical variables, including blood ammonia, and an oral primed-continuous protocol of L-1-(13)C-Leucine was performed. Blood ammonia concentrations above normal values (35 µmol/L) were observed at leucine intakes >550 mg kg(-1) day(-1). Leucine oxidation measured as a F(13)CO2 (rate of label tracer oxidation) increased with increasing leucine intakes and started to plateau after 450 mg kg(-1) day(-1). Two-phased linear regression analysis of the F(13)CO2 data revealed a breakpoint of 431 mg kg(-1) day(-1) (R (2) = 0.73), suggesting that the upper limit to oxidize leucine was reached at that point. Taking the data together the upper limit for leucine intake in healthy elderly could be set similar to young men at 500 mg kg(-1) day(-1) or ~35 g/day for an individual weighing 70 kg.

Dietary fibre-rich resistant starches promote ammonia detoxification in the human colon as measured by lactose-[¹5N2]ureide.

Three resistant starches (RSs), namely fibre of potatoes (FP), wrinkle pea starch (WPS), and high amylose maize starch (HAMS) with different dietary fibre contents, were supplemented in adults to evaluate their effects on urinary nitrogen and ammonia excretion as well as on faecal nitrogen excretion by means of lactose-[(15)N2]ureide ((15)N-LU) degradation. Twenty subjects received a regular diet either without or with the supplementation of FP, WPS, and HAMS in a randomized order. After administration of (15)N-LU, urine and faeces were collected over 48 and 72 h, respectively, whereas blood was collected after 6 h. The (15)N-abundances were measured by isotope ratio mass spectrometry. In comparison to the dry run, supplementation with RS significantly lowered renal (15)N-excretion (dry run: 43.2%, FP: 34.6%, WPS: 37.9%, HAMS: 36.4%) as well as the corresponding (15)NH3-excretion (dry run: 0.08%, FP: 0.06%, HAMS: 0.05%), clearly indicating a reduced colonic nitrogen generation at high dietary fibre intake.

Effects on milk urea concentration, urine output, and drinking water intake from incremental doses of potassium bicarbonate fed to mid-lactation dairy cows.

Large variation exists in the potassium content of dairy cow feeds and also within a feed type due to soil type and fertilization. Increased ration K concentration causes a subsequent increase in urinary volume and could be expected to also lower milk urea concentration. Six multiparous mid-lactation Swedish Red dairy cows, all fitted with rumen cannulas, were subjected to 3 different levels of K intake in a Latin square experiment with three 2-wk periods to evaluate the effects on concentrations of milk urea and rumen ammonia, urinary output, and drinking water intake. The treatments were achieved by K supplementation on top of a low-K basal ration fed at individual allowances fixed throughout the experiment. The basal ration, consumed at 20.2 kg of dry matter (DM)/d, provided 165 g of crude protein/kg of DM and consisted of grass silage, concentrates, and urea in the proportions 39.3:60.0:0.7 on a DM basis. Potassium bicarbonate supplementation was 0, 616, and 1,142 g/d, respectively, to give total ration K concentrations that were low (LO; 12 g/kg of DM), medium (MED; 23 g/kg of DM), or high (HI; 32 g/kg of DM). Production and composition of milk was not affected by treatment. A linear effect on milk urea concentration was detected, being 4.48, 4.18, and 3.77 mM for LO, MED, and HI, respectively, and a linear tendency for rumen ammonia concentration with 6.65, 6.51, and 5.84 mg of NH3-N/dL for LO, MED, and HI, respectively. Milk urea concentration peaked about 3h after the rumen ammonia peak from the morning feeding, at a level 1.3mM over the baseline. Urinary urea excretion declined linearly (105, 103, and 98 g of urea-N/d for LO, MED, and HI, respectively). Linear increases occurred in urinary output (0.058 ± 0.001 kg of urine/g of K intake; no intercept; coefficient of determination=0.997) and drinking water intake (65.9 ± 2.02 + 0.069 ± 0.004 kg of water/g of K intake; coefficient of determination=0.95). Urinary K concentration leveled off at 12.4 g/L. Urinary creatinine excretion was not affected by K addition, but allantoin excretion increased linearly by 27% from LO to HI, suggesting increased rumen microbial growth. Rumen pH, acetate proportion of total volatile fatty acids, and digestibility of DM, organic matter, and neutral detergent fiber increased linearly with increasing potassium intake. We concluded that increased ration K concentration lowers milk urea concentration with a magnitude significant for the interpretation of milk urea values, but other sources of variation, such as sampling time relative to feeding, may be even more important.

Comparison of a wheat-based diet supplemented with purified {beta}-glucans, with an oat-based diet on nutrient digestibility, nitrogen utilization, distal gastrointestinal tract composition, and manure odor and ammonia emissions from finishing pigs.

It was hypothesized that supplementation of an oat-extracted mixed-linkage (1 → 3), (1 → 4)-ß-d-glucan (ß-glucans) to a wheat-based diet may beneficially mitigate manure odor and ammonia emissions associated with intensive pig production, without depressing nutrient digestibility as has been observed with oat-based diets. An experiment was conducted to investigate the effect of dietary ß-glucan source and the inclusion of an enzyme composite containing ß-glucanase on energy and nutrient digestibility, N utilization, distal gastrointestinal tract (GIT) fermentation, and manure emissions from finisher boars. Twenty-eight boars (BW = 74.2 ± 3.6 kg) were assigned to 1 of 4 dietary treatments (n = 7/treatment): 1) an oat-based diet (oat), 2) an oat diet + enzyme composite (OE), 3) a wheat-based diet + purified ß-glucans (WG), and 4) a wheat-based diet + purified ß-glucans + enzyme composite. The wheat-based diets containing purified ß-glucans were formulated to contain concentrations of total ß-glucans comparable with the oat-based diet. Consumption of the WG diet resulted in a greater digestibility of GE (P = 0.001) and an increase in the urine:feces N excretion ratio (P = 0.049) compared with the oat diet. In the distal GIT, pigs offered the WG diet contained fewer bifidobacteria (P = 0.027) and lactobacilli (P = 0.050) compared with the oat diet. Pigs offered the WG diet had increased manure odor emissions compared with the oat diet (P = 0.023). In conclusion, although supplementing wheat-based diets with extracted oat-ß-glucan did not reduce nutrient digestibility, there was a negligible effect in beneficially influencing manure emissions from pigs when compared with a conventional oat formulation.

Effect of frequency and amount of rumen-degradable intake protein supplementation on urea kinetics and microbial use of recycled urea in steers consuming low-quality forage.

We evaluated the effect of frequency and amount of rumen-degradable intake protein (DIP) on urea kinetics in steers consuming prairie hay. Five ruminally and duodenally fistulated steers (366 kg of BW) were used in a 5 x 5 Latin square and provided ad libitum access to low-quality prairie hay (4.7% CP). Casein was provided daily in amounts of 61 and 183 mg of N/kg of BW (61/d and 183/d) and every third day in amounts of 61, 183, and 549 mg of N/kg of BW per supplementation event (61/3d, 183/3d, and 549/3d). Periods were 18-d long with 9 d for adaptation and 9 d for collection. Steers were in metabolism crates for total collection of urine and feces. Jugular infusion of (15)N(15)N-urea followed by determination of urinary enrichment of (15)N(15)N-urea and (14)N(15)N-urea was used to determine urea kinetics. Treatment means were separated to evaluate the effects of increasing DIP supplementation and the effects of frequency at the low (61/d vs. 183/3d) and at the high (183/d vs. 549/3d) amounts of DIP provision. Forage OM and total digestible OM intakes were linearly (P < or = 0.05) increased by increasing DIP provision but were not affected by frequency of supplementation at either the low or high amounts. Production and gut entry of urea linearly (P < or = 0.006) increased with DIP provision and tended to be greater (P < or = 0.07) for 549/3d than 183/d but were not different between 61/d and 183/3d. Microbial N flow to the duodenum was linearly (P < 0.001) increased by increasing DIP provision. Additionally, 183/d resulted in greater (P = 0.05) microbial N flow than 549/3d. Incorporation of recycled urea-N into microbial N linearly (P = 0.04) increased with increasing DIP. Microbial incorporation of recycled urea-N was greater for 549/3d than 183/d, with 42 and 23% of microbial N coming from recycled urea-N, respectively. In contrast, there was no difference due to frequency in the incorporation of recycled urea-N by ruminal microbes at the low level of supplementation (i.e., 61/d vs. 183/3d). This study demonstrates that urea recycling plays a substantial role in the N supply to the rumen and to the animal, particularly in steers supplemented infrequently with high levels of protein.

Effect of rumen-degradable intake protein supplementation on urea kinetics and microbial use of recycled urea in steers consuming low-quality forage.

We evaluated the effect of increasing amounts of rumen-degradable intake protein (DIP) on urea kinetics in steers consuming prairie hay. Ruminally and duodenally fistulated steers (278 kg of BW) were used in a 4 x 4 Latin square and provided ad libitum access to low-quality prairie hay (4.9% CP). The DIP was provided as casein dosed ruminally once daily in amounts of 0, 59, 118, and 177 mg of N/kg of BW daily. Periods were 13 d long, with 7 d for adaptation and 6 d for collection. Steers were in metabolism crates for total collection of urine and feces. Jugular infusion of (15)N(15)N-urea, followed by determination of urinary enrichment of (15)N(15)N-urea and (14)N(15)N-urea was used to determine urea kinetics. Forage and N intake increased (linear, P < 0.001) with increasing DIP. Retention of N was negative (-2.7 g/d) for steers receiving no DIP and increased linearly (P < 0.001; 11.7, 23.0, and 35.2 g/d for 59, 118, and 177 mg of N/kg of BW daily) with DIP. Urea synthesis was 19.9, 24.8, 42.9, and 50.9 g of urea-N/d for 0, 59, 118, and 177 mg of N/kg of BW daily (linear, P = 0.004). Entry of urea into the gut was 98.9, 98.8, 98.6, and 95.9% of production for 0, 59, 118, and 177 mg of N/kg of BW daily, respectively (quadratic, P = 0.003). The amount of urea-N entering the gastrointestinal tract was greatest for 177 mg of N/kg of BW daily (48.6 g of urea-N/d) and decreased (linear, P = 0.005) to 42.4, 24.5, and 19.8 g of urea-N/d for 118, 59, and 0 mg of N/kg of BW daily. Microbial incorporation of recycled urea-N increased linearly (P = 0.02) from 12.3 g of N/d for 0 mg of N/kg of BW daily to 28.9 g of N/d for 177 mg of N/kg of BW daily. Provision of DIP produced the desired and previously observed increase in forage intake while also increasing N retention. The large percentage of urea synthesis that was recycled to the gut (95.9% even when steers received the greatest amount of DIP) points to the remarkable ability of cattle to conserve N when fed a low-protein diet.

Diffusion pollution from livestock and poultry rearing in the Yangtze Delta, China.

BACKGROUND: The Yangtze Delta is one of the most developed regions in China and includes Shanghai, eight cities in Jiangsu province and eight cities in Zhejiang province. Meat consumption in this region has increased with economic growth, and most of the consumed meat is produced locally. The water quality of surface waters has deteriorated in recent years. An example was the huge blue-green algae bloom in Tai Lake in late May 2007, which affected millions of people's daily drinking water. However, animal husbandry is considered to be one of the main pollution sources. METHODS: Pollutants (NH3-N, total phosphorus (TP), and total nitrogen (TN)) excreted by livestock and poultry, and the resultant COD (chemical oxygen demand) and BOD (biochemical oxygen demand), were estimated using two different methods based on different data sets. RESULTS: The number of livestock and poultry has remained stable in the Yangtze Delta over the four years from 1999 to 2002, with the average number of pigs, cattle, sheep and poultry being 21.1 M, 0.4 M, 7.7 M and 597.6 M, respectively. Pollutants in livestock and poultry excreta estimated by Method I were: 0.12 Mt NH3-N, 0.11 Mt TP and 0.29 Mt TN, resulting in COD and BOD of 1.34 Mt and 1.30 Mt, respectively, while the estimations based on Method II were: 0.18 Mt NH3-N, 0.15 Mt TP and 0.40 Mt TN, resulting in COD and BOD of 1.95 Mt and 1.80 Mt, respectively. DISCUSSION: Pollutants excreted annually by livestock and poultry in the Yangtze Delta are estimated to be: 0.17 Mt NH3-N, 0.16 Mt TP and 0.42 Mt TN, giving rise to a COD of 1.86 Mt and a BOD of 1.72 Mt. Approximately 25% of this pollution was estimated to enter water bodies, which means that the annual pollutant load is 43,700 t NH3-N, 39,400 tTP, 104,600t TN with a COD of 465,000 tand a BOD of 430,100 t. Pollutants from animal husbandry were similar in magnitude to those from industrial wastewater. Pigs produced the most pollution, followed by poultry, cattle and sheep. The pollution load from animal husbandry in the Yangtze Delta is about twice the average level of the whole of China. CONCLUSIONS: Domestic wastewater was the main pollution source in the Yangtze Delta, followed by pollution from raising livestock and poultry and from industrial wastewater. The pollution load in Shanghai and Jiaxing were the greatest, followed by 7 cities of Jiangsu province (except Suzhou) and other cities of Zhejiang province and Suzhou. Pigs and poultry produced about 90% of the total pollutants from animal husbandry. RECOMMENDATIONS AND PERSPECTIVES: The local governments, especially in Shanghai and Jiaxing, should focus their attention on the pollution produced by livestock and poulrry. Controlling pollution from pigs and poultry will have the greatest impact in this region. Control of pollution will be facilitated by the development of large-scale livestock and poultry farming units and a shift away from small scale husbandry.

Frequent intravenous pulses of growth hormone together with glutamine supplementation in prolonged critical illness after multiple trauma: effects on nitrogen balance, insulin resistance, and substrate oxidation.

OBJECTIVES: To estimate the efficacy and metabolic effects of growth hormone substitution as intravenous pulses together with alanyl-glutamine supplementation and tight blood glucose control in prolonged critical illness. DESIGN: Prospective double-blind, randomized trial with open-label control arm. SETTING: Intensive care unit of tertiary level hospital. PATIENTS: Thirty multiple trauma patients (median Injury Severity Score 34). INTERVENTIONS: Patients were randomized, at day 4 after trauma, to receive intravenous alanyl-glutamine supplementation (0.3 g/kg x day(-1) from day 4 until day 17) and intravenous growth hormone (administered days 7-17, full dose 50 microg/kg x day(-1) from day 10 onward) (group 1, n = 10) or alanyl-glutamine and placebo (group 2, n = 10). Group 3 (n = 10) received isocaloric isonitrogenous nutrition (proteins 1.5 g/kg x day(-1)) without alanyl-glutamine. MEASUREMENTS AND MAIN RESULTS: Cumulative nitrogen balance for the whole study period was -97 +/- 38 g of nitrogen for group 1, -193 +/- 50 g of nitrogen for group 2, and -198 +/- 77 g of nitrogen for group 3 (p < .001). This represents a daily saving of 300 g of lean body mass in group 1. Insulin-mediated glucose disposal, during euglycemic clamp, as a measure of insulin sensitivity, significantly worsened between days 4 and 17 in group 1 but improved in groups 2 and 3. Group 1 required significantly more insulin to control blood glucose, resulting in higher insulinemia (approximately 70 mIU in group 1 vs. approximately 25 mIU in groups 2 and 3). Despite this, growth hormone treatment caused an increase in plasma nonesterified fatty acid (approximately 0.5-0.6 mM in group 1 in comparison with approximately 0.2-0.3 mM in groups 2 and 3) but did not influence lipid oxidation. There were no differences in morbidity, mortality, or 6-month outcome among the groups. CONCLUSIONS: Treatment with frequent intravenous pulses of low-dose growth hormone together with alanyl-glutamine supplementation improves nitrogen economy in patients with prolonged critical illness after multiple trauma but worsens insulin sensitivity. Tight blood glucose control is possible but requires higher doses of insulin.

Factors affecting struvite (MgNH4PO4.6H2O) crystallization in feline urine.

Factors affecting struvite, a magnesium-ammonium-phosphate complex (MgNH(4)PO(4).6H(2)O), in feline urine were evaluated. Incubation of just "urine mineral (UM)" solution, in which mineral concentrations are compatible with those in feline urine, for 4 h at 37 degrees C did not induce the formation of crystals. Similarly, incubation of urine alone did not produce crystals. However, struvite crystals were formed by the addition of urine to UM solution. Mg, NH(3) and P were all required for urine-induced struvite crystallization. The lower molecular weight (LMW) fraction of urine was essential for struvite crystal formation, and the higher molecular weight (HMW) fraction enhanced formation of LMW-induced struvite crystals. The effects of urine proteins further fractionated by column chromatography were examined. A protein at >250 kDa and cauxin, a major urine protein recently identified as a regulator of felinine production, potentiated struvite crystal formation induced by the LMW fraction. In contrast, Tamm-Horsfall glycoprotein, a urine protein thought to promote struvite crystallization, did not have this activity. The present study reveals a novel mechanism of feline struvite crystallization.

The influence of inulin on the absorption of nitrogen and the production of metabolites of protein fermentation in the colon.

In the present study, the production and fate of bacterial metabolites in the colon were investigated in a direct way using two substrates labelled with stable isotopes: lactose [(15)N,(15)N]ureide as a source of labelled ammonia and egg proteins intrinsically labelled with [(2)H4]tyrosine as a precursor of [(2)H4]p-cresol. Both ammonia and phenolic compounds are believed to be carcinogenic. Stimulation of carbohydrate fermentation in order to prevent accumulation of these toxic metabolites was induced by inclusion of inulin in a test meal or by addition of inulin to the daily diet, allowing us to distinguish between changes induced by the actual presence of a fermentable carbohydrate and effects caused by a long-term dietary intervention. When a single dose of inulin was administered together with the labelled substrates, a significant increase in faecal (15)N excretion, accompanied by a proportional decrease in urinary (15)N excretion was observed, probably reflecting an enhanced uptake of ammonia for bacterial biosynthesis, since an increased concentration of labelled N in bacterial pellets was found. A statistically significant reduction of urinary [(2)H4]p-cresol excretion was also noted. Upon supplementation of inulin to the daily diet during 4 weeks, however, only a tendency towards decreased urinary excretion of both labelled and unlabelled p-cresol was noted. Further studies are warranted to confirm these results in a larger cohort.

[Pathophysiology and diagnosis of renal tubular acidosis]. / Pathophysiologie und Diagnostik renal tubulärer Azidosen.

Intrinsic defects in tubular transport mechanisms of the kidney may cause impairment of urinary acidification or a loss of base equivalents, thereby inducing systemic metabolic acidosis. Different types of this disorder termed renal tubular acidosis (RTA) can be distinguished based on the localization of the disturbance along the nephron (proximal vs. distal) and their association with potassium transport (hypo-/hyperkalemic). Except for the proximal type RTA results in positive acid balance and negatively impacts on bone metabolism and the formation of kidney stones. The diagnosis is based on analysis of acid/base status, urinary pH and determination of ammonium excretion after an oral acid load. Both functional defects of specific tubular transport mechanisms and global impairment of renal tubular function can be causative of RTA. Their therapy is based on treatment of the primary disease process and correction of acidosis by alkali supplementation.

Short-term emissions of ammonia and carbon dioxide from cattle urine contaminated tropical grassland microcosm.

The study was designed to understand the emissions of ammonia (NH(3)) and carbon dioxide (CO(2)) from a single cattle urination event on a tropical grassland and underline the significance of the emissions in the context of huge animal population grazing on large pasture areas in some countries. Emissions of ammonia (NH(3)) and carbon dioxide (CO(2)) were monitored for three weeks from a tropical grassland (dominated by Cynodon dactylon Pers.) microcosm contaminated with cow and buffalo urine. The grassland microcosms were treated with urine (50 and 100 ml of each) only once and irrigated with water once every week. Ammonia was sampled by an automatic sampling system comprising of a vacuum pump, three-way stopcocks and rubber tubing and an impinger containing suitable absorbing solution (H(2)SO(4)), connected to the tubing suitably. The sampled gas, after sucked by the vacuum pump and absorbed in H(2)SO(4), was allowed to enter the closed microcosm again maintaining internal pressure of the microcosm. Carbon dioxide was sampled by absorption in an alkali (NaOH) trap inside the microcosm. Both NH(3) and CO(2) emissions were highly variable temporally and there was no continuous increasing or decreasing emission trend with time. Respectively, 45 and 46% of total NH(3)-N were emitted within first 48 h from 50 and 100 ml cow urine application while the corresponding values for buffalo urine were 34 and 32%. Total NH(3)-N emissions, integrated for sampling days (i.e. 1, 2, 3, 4, 6, 15, 18 and 21st) were 11 and 6% in cow and 8 and 5% in buffalo urine, of the total-N added through 50 and 100 ml urine samples. Carbon dioxide emissions were standardized at 25 degrees C by using a suitable formula which were lower than actual emissions at actual soil temperature (> 25 degrees C). Carbon dioxide emission rates were classified on the basis of soil repiratory classification and classes ranged from moderately low soil activity up to unusually high soil activity, the latter observed only on very few sampling days. Grasses in the microcosm had shown appreciable growth after urine application. Although variable and somewhat unpredictable, emissions were appreciable and that too only from a patch of single urination, indicating to the huge magnitude of total emissions under the scenario of thousands of cattle grazing on hundreds of acres of grasslands in a tropical country.

Effect of potassium salts in rats adapted to an acidogenic high-sulfur amino acid diet.

Low-grade metabolic acidosis, consecutive to excessive catabolism of sulfur amino acids and a high dietary Na:K ratio, is a common feature of Western food habits. This metabolic alteration may exert various adverse physiological effects, especially on bone, muscle and kidneys. To assess the actual effects of various K salts, a model of the Westernised diet has been developed in rats: slight protein excess (20 % casein); cations provided as non-alkalinising salts; high Na:K ratio. This diet resulted in acidic urine (pH 5.5) together with a high rate of divalent cation excretion in urine, especially Mg. Compared with controls, K supplementation as KCl accentuated Ca excretion, whereas potassium bicarbonate or malate reduced Mg and Ca excretion and alkalinised urine pH (up to 8). In parallel, citraturia was strongly increased, together with 2-ketoglutarate excretion, by potassium bicarbonate or malate in the diet. Basal sulfate excretion, in the range of 1 mmol/d, was slightly enhanced in rats fed the potassium malate diet. The present model of low-grade metabolic acidosis indicates that potassium malate may be as effective as KHCO3 to counteract urine acidification, to limit divalent cation excretion and to ensure high citrate concentration in urine.

Excretion of major odor-causing and acidifying compounds in response to dietary supplementation of chicory inulin in growing pigs.

The excretion of major odor-causing and acidifying compounds in response to dietary supplementation of chicory inulin extract was investigated with six Yorkshire barrows, with an average initial BW of 30 kg, according to a balanced two-period cross-over design. The animals were fed a control diet containing no inulin extract and a treatment diet with 5% inulin extract (as-fed basis) at the expense of cornstarch. Each diet was formulated (as-fed basis) to contain 16% CP from corn (51%) and soybean meal (29%). Each experimental period lasted 14 d, with 10 d for dietary adaptation and 4 d for collection of fecal and urine samples. The fecal samples were analyzed for four major classes of odor-causing and acidifying compounds: 1) VFA; 2) N-containing compounds, including total N and ammonia; 3) volatile sulfides measured as hydrogen sulfide units; and 4) phenols and indoles, including p-cresol, indole, and skatole. Supplementation of chicory inulin at 5% had no effects on the fecal excretion of VFA (P = 0.29), ammonia (P = 0.96), total volatile sulfides (P = 0.56), p-cresol (P = 0.56), and indole (P = 0.75). Fecal excretion of total N (inulin = 6.13 vs. control = 5.10 g/kg DMI) was increased (P < 0.05), whereas urinary total N excretion (inulin = 15.1 vs. control = 16.4 g/[pig x d]) was not affected (P = 0.17) by the inulin supplementation compared with the control group. Furthermore, fecal excretion of skatole (inulin = 9.07 vs. control = 18.93 mg/kg DMI) was decreased (P < 0.05) by the inulin supplementation compared with the control group. In conclusion, dietary supplementation of 5% chicory inulin extract is effective in decreasing the fecal excretion of skatole in growing pigs fed corn and soybean meal diets.

Changes in the composition of the urine of yellow-vented bulbuls (Pycnonotus xanthopygos): the effects of ambient temperature, nitrogen, and water intake.

Uricotely (uric acid >50% of urinary nitrogen) in birds was once considered ubiquitous. However, Anna's hummingbirds (Calypte anna) have been shown to be an exception to this rule; under conditions of low ambient temperature (T(a)) and on a nitrogen-free diet, they increased their water intake and often became ammonotelic (ammonia >50% of urinary nitrogen). Our aim was to identify the effects of nitrogen intake, water intake, and T(a) on the ammonia excretion of yellow-vented bulbuls (Pycnonotus xanthopygos). We chose this predominantly frugivorous species because many of the characteristics of nectarivores that were used to explain increased ammonia excretion by C. anna are also characteristics of frugivorous birds. We assayed ureteral urine composition in eight yellow-vented bulbuls (P. xanthopygos), each randomly allocated a diet of 20% (0.6 M) sucrose solution supplemented by either 1.03 g/L or 7.23 g/L soy protein and held at a T(a) of either 28 degrees C or 10 degrees C. Food, and therefore water, intake rates varied with nitrogen intake but not with T(a). Food intake increased significantly with decreased nitrogen intake, while concentrations of all the excretory compounds in the urine (P<0.05) decreased; yet their proportions in the urine did not change significantly. The lower T(a) had no significant effect on food intake or on the concentration of uric acid. However, at 10 degrees C, the ammonia and urea concentrations increased (P<0.05), and this led to a significant increase in the proportion of ammonia in the urine. Our results demonstrate that, when bulbuls are exposed to low T(a), they are able to save energy by increasing the proportion of the ammonia in their urine.

Proximal renal tubular peptide catabolism, ammonia excretion and tubular injury in patients with proteinuria: before and after lisinopril.

1. Progression to renal failure may be linked to the degree of proteinuria through tubulo-interstitial mechanisms. However, there are no data in man on the kinetics of proximal renal tubular protein catabolism or markers of tubular injury before and after lisinopril. We developed a method to allow such studies, and found increased tubular catabolism of 99mTc-labelled aprotinin (Trasylol) in patients with nephrotic range proteinuria which was associated with increased ammonia excretion. 2. In this study, 10 patients with mild renal impairment (51Cr-EDTA clearance 63.7 +/- 8.3 ml.min-1.1.73 m-2) and heavy proteinuria (8.2 +/- 2.3 g/ 24 h) were given lisinopril (10-20 mg) for 6 weeks. Renal tubular catabolism of intravenous aprotinin was measured before and after lisinopril by renal imaging and urinary excretion of the free radiolabel over 26 h. Fractional degradation was calculated from these data. Fresh timed urine collections were also analysed for ammonia excretion every fortnight from 6 weeks before treatment. Total urinary N-acetyl-beta-D-glucosaminidase and the more tubulo-specific N-acetyl-beta-D-glucosaminidase 'A2' isoenzyme were also measured. 3. After lisinopril proteinuria fell significantly as expected (from 9.5 +/- 1.6 to 4.5 +/- 1.0 g/24 h, P < 0.01). This was associated with a reduction in metabolism over 26 h (from 1.7 +/- 0.1 to 1.2 +/- 0.1% dose/h, P < 0.01) and in fractional degradation of aprotinin (from 0.08 +/- 0.02 to 0.04 +/- 0.007/h, P < 0.04). Ammonia excretion also fell significantly (from 1.2 +/- 0.1 to 0.6 +/- 0.1 mmol/h, P < 0.0001), as did both total urinary N-acetyl-beta-D-glucosaminidase (P < 0.0001) and the N-acetyl-beta-D-glucosaminidase 'A2' isoenzyme (P < 0.015). These observations after lisinopril treatment have not been described previously. There was no significant change in blood pressure nor in glomerular haemodynamics.

Usefulness of short-term urine collection in the nutritional monitoring of low birthweight infants.

To establish adequacy of urine collection times shorter than 24h in the metabolic monitoring of low birthweight infants, we collected urine for 24 h in 39 LBW infants during the third and fourth week of life. All urine voidings over the 24-h period were separately collected, the volume of each sampling and the time of voiding were recorded, and 20% of the volume was removed for pooling. All individual and pooled samples were analysed for total nitrogen, urea and ammonia, alpha-amino nitrogen, creatinine, sodium, potassium, calcium and phosphorus, and for each compound the ratio to 1 mol creatinine was established. Individual sample results were "pooled" to obtain 3-, 6- and 12-h period excretion and than related to the 24-h excretion as measured in the pooled 24-h sample. As the volume of urine obtained in any 6-h collecting period depended on the time of sampling (06:00-12:00 h, 17.5+/-3.1% of total; 12:00-18:00 h, 31.6+/-5.1% of total; 18:00-24:00 h, 25.6+/-3.1% of total; and 0:00-06:00h, 25.3+/-2.9% of total), calculations were based on samples obtained from 18:00 to 06:00 h. The correlation between results of 3- and 24 h-collection periods was weakest, while results of the 6-h collection correlated highly with the total daily excretion (r = between 0.82 and 0.93 for the different compounds) and the correlation was only slightly better when the 12-h collection period was considered. The correlation between the mean molar substrate/creatinine ratio of all individual samples of a 24-h collecting period and the and total daily excretion of the respective substrate was weaker (r = between 0.46 and 0.76 for the different compounds) than the correlation between the results of a 6-h collecting period and the daily excretion is not as stable than in later life. The data indicate that 6-h urine sampling may be sufficient for metabolic monitoring of LBW infants. By contrast, urinary substrate/creatinine ratios are not good markers of the daily excretions of the respective substrate during the first weeks of life.

The relationship among dietary undetermined anion, acid-base balance, and nutrient metabolism in swine.

Dietary undetermined anion (dUA) reflects, in part, the net acid load contributed by the diet. Although dUA is known to influence performance and nutrient metabolism of swine, a lack of knowledge impairs its application to diet formulation. This study was undertaken to separate the effects of dUA from the individual electrolytes that constitute its calculation. Eighteen 35-kg pigs were fitted with indwelling venous catheters and fed one of three barley and soybean meal-based diets: a control diet (C), an acidogenic diet containing calcium chloride (A), or a compensated acidogenic diet containing alkaline salts of sodium and potassium, as well as calcium chloride (CA). Compared with diet C, diet A lowered (P < .05) blood pH, bicarbonate, and base excess and increased (P < .05) urinary ammonium, titratable acid (TA), and net acid excretion (NAE). Diet CA returned blood acid-base values to normal and reduced urinary ammonium, TA, and NAE relative to diet A. Total nitrogen balance was unaffected by diet. Diet CA increased (P < .05) water intake and urine output. Diet A, but not CA, increased (P < .05) serum ionized Ca and C1. Apparent Ca and S digestibility and retention were reduced by diet A, but not by CA. Sodium retention was enhanced (P < .05) by diets A and CA; potassium retention was impaired (P < .05) by CA. Dietary UA altered systemic and renal acid-base balance in pigs. Mineral, but not nitrogen, metabolism was affected by both dUA and specific ion effects.