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PubMed1996

In vivo formation of mutagens by intraperitoneal administration of polycyclic aromatic hydrocarbons in animals during exposure to nitrogen dioxide.

Consumption of fossil fuels has increased indoor and outdoor concentrations of polycyclic aromatic hydrocarbons (PAHs) and nitrogen dioxide (NO2). To study the combined effect of PAH administration and NO2 exposure on mutagenicity of urine from animals we injected 400 mg/kg body wt i.p. one of five kinds of PAH (pyrene, fluoranthene, fluorene, anthracene and chrysene) into ICR mice, Wistar rats, Syrian golden hamsters or Hartley guinea pigs after exposure to 20 p.p.m. NO2 gas for 24 h and then exposed the animals to NO2 gas for an additional 24 h. During the latter 24 h we collected the urine and assayed its mutagenicity with the Ames Salmonella strains after treatment with beta-glucuronidase and arylsulfatase and extraction with dichloromethane. The urine from mice treated with both PAH and NO2 showed high mutagenicity for Salmonella typhimurium strains TA98 and TA100, whereas the urine from mice treated with PAH and air showed almost no mutagenic activity. The mutagenicity was decreased in nitroreductase- and acetyltransferase-deficient strains TA98NR and TA98/1,8-DNP6 respectively. Treatment with a mixture of 20% of each of the five kinds of PAH and NO2 augmented the urinary mutagenicity of mice 1.5-fold. The urine from hamsters treated with pyrene or fluoranthene and NO2 was also highly mutagenic, but that from rats or guinea pigs was not very mutagenic. The mutagenicity was also decreased in strains TA98NR and TA98/1,8-DNP6. These results suggest that the urine contains nitro compounds and that the nitration of PAHs occurs in the body of animals under exposure to NO2 gas. Actually, the nitrated metabolites of pyrene, 1-nitro-6/8-hydroxypyrene and 1-nitro-3-hydroxypyrene, were detected in the urine from mice treated with pyrene under exposure to NO2 gas. To elucidate the mechanism of in vivo nitration, NO2 (20 p.p.m.) was bubbled through 50 mM Tris-HCl buffer (pH 7.4) or dichloromethane solution containing pyrene or 1-hydroxypyrene (10 microg/ml). Pyrene was not nitrated by NO2 in either aqueous or organic solutions. However, 1-hydroxypyrene was changed to nitrohydroxypyrenes by NO2 in the Tris-HCl buffer, but not in the organic solution. Ascorbic acid, alpha-tocopherol, glutathione oleic acid and hemoglobin were found to inhibit the nitration of 1-hydroxypyrene in aqueous solution. The urinary mutagenicity of mice treated with both pyrene and NO2 was also decreased by oral administration of ascorbic acid and alpha-tocopherol. These results suggest that 1-hydroxypyrene is nitrated by an ionic reaction in the animal body after hydroxylation of pyrene in the liver.

Animals↗
PubMed2004

Effect of nitrogen limitation and surplus upon trehalose metabolism in wine yeast.

Trehalose metabolism in yeast has been related to stress and could be used as a stress indicator. Winemaking conditions are stressful for yeast and understanding trehalose metabolism under these conditions could be useful for controlling alcoholic fermentation. In this study, we analysed trehalose metabolism of a commercial wine yeast strain during alcoholic fermentation by varying the nitrogen levels from low (below adequate) to high (excess). We determined trehalose, nitrogen, sugar consumption and expression of NTH1, NTH2 and TPS1. Our results show that trehalose metabolism is slightly affected by nitrogen availability and that the main consumption of nitrogen occurs in the first 24 h. After this period, nitrogen is hardly taken up by the yeast cells. Although nitrogen and sugar are still available, no further growth is observed in high concentrations of nitrogen. Increased expression of genes involved in trehalose metabolism occurs mainly at the end of the growth period. This could be related to an adaptive mechanism for fine tuning of glycolysis during alcoholic tumultuous fermentation, as both anabolic and catabolic pathways are affected by such expression.

Fermentation↗
PubMed2006

Effect of natural and laboratory diet on O : N ratio in juvenile lobsters (Homarus americanus).

Oxygen consumption and ammonia excretion rates of juvenile lobsters spanning the size range from shelter-restricted to vagile (7-60 mm CL, carapace length) were measured. There are no significant size-dependent break points in the slope of oxygen consumption or nitrogen excretion rates versus weight in freshly caught wild or laboratory fed lobsters. This suggests that there are no inherent changes in energy metabolism in juvenile lobster in the 7-60 mm CL range (stage V to adolescent lobsters), despite major behavioral shifts related to foraging and shelter use. In addition, the O : N ratio of freshly caught wild lobsters (15.7+/-7.4, mean+/-S.D.) is not significantly different from that of lobsters fed brown algae (13.4+/-4.9) or a mixed carbohydrate/protein diet (13.7+/-6.8) in lab. The O : N ratio of wild lobsters is significantly higher than lobsters fed a high protein diet (7.5+/-2.5) in the lab. This suggests that carbohydrates, particularly algal-derived carbohydrates, make up a significant portion of the metabolic fuel of wild juvenile lobsters from settlement through adolescence.

Ammonia↗
PubMed2002

A supervisory control system for optimising nitrogen removal and aeration energy consumption in wastewater treatment plants.

A fuzzy logic supervisory control system for optimising nitrogen removal and aeration energy consumption has been developed. This control system allows optimising and controlling the dissolved oxygen (DO) concentration in the aerobic reactors, the blowers discharge pressure and the effluent ammonia and nitrate concentrations. DO is controlled by adjusting control valve opening and blower discharge pressure is controlled by modifying rotational speed of the blowers. Optimum nitrification/denitrification is achieved by modifying the DO set point in the last aerobic reactor and the internal recirculation. This system has been tested by simulation in a Bardenpho process using the Activated Sludge Model No2. A significant improvement in stability on the activated sludge process is achieved. Moreover, significant energy saving has been achieved with this control strategy.

Aerobiosis↗
PubMed1985

Relationship between food consumption and energy and nitrogen utilisation by chicks given varying amounts of standard and leucine-, isoleucine- and valine-deficient diets.

The effect of different amounts of food, varying from below to above the rate of voluntary intake, was studied in chicks using a standard diet and diets containing only half the recommendation concentrations of leucine, isoleucine or valine. Irrespective of diet the body weight gain of the chicks increased with increasing food consumption. The body weight gain of chicks given the leucine-deficient diet was similar to that of chicks given the same amount of the standard diet. In contrast, the body weight gains of chicks given either the valine- or isoleucine-deficient diet were significantly less than that of chicks given the same amount of the standard diet. When the food intakes of the birds were similar the differences in body protein and water contents of the birds fed the different diets reflected differences in body weight gains, whereas body fat content was affected in the reverse manner. Retention and retention rate of dietary energy increased as food consumption increased. This was particularly evident in chicks given the isoleucine-deficient diet, followed by those given the valine-, leucine-deficient and standard diets. For all diets, the amounts of nitrogen retained and nitrogen retention rate (N retained/N consumed) increased in line with body weight gain. The metabolisable energy values of the diets were similar, except for the isoleucine-deficient diet which had a significantly higher metabolisable energy value than the standard valine-deficient diets.

Amino Acids, Essential↗
PubMed1987

Dietary intake and nitrogen balance in athletes with and without consumption of a protein supplement.

Nitrogen balance and nutrient intake were assessed in five males and four females involved in body building and weight training when consuming their habitual diet and whilst half the group were taking a protein supplement. Pre-supplementation nutrient intakes varied greatly but intakes of some nutrients were lower than RDAs (DHSS, 1979). Protein supplementation did not significantly improve nutrient intake, and it was concluded that it is unlikely to improve nitrogen retention because it does not significantly increase nitrogen intake.

Adult↗
PubMedDate not supplied

Development of a phenomenological modeling approach for prediction of growth and xanthan gum production using Xanthomonas campestris.

An unstructured kinetic model for xanthan production is described and fitted to experimental data obtained in a stirred batch reactor. The culture medium was composed of several nitrogen sources (soybean hydrolysates, ammonium and nitrate salts) consumed sequentially. The model proposed is able to describe this sequential consumption of nitrogen sources, the consumption of inorganic phosphate and carbon, the evolution of biomass, and production of xanthan. The parameter estimation has been performed by fitting the kinetic model in differential form to experimental data. Runs of the model for simulating xanthan gum production as a function of the initial concentration of inorganic phosphate have shown the positive effect of phosphate limitation on xanthan yield, though diminishing rates of production. The model was used to predict the kinetic parameters for a medium containing a 2-fold lower initial phosphate concentration. When tested experimentally, the measured fermentation parameters were in close agreement with the predicted model values, demonstrating the validity of the model.

Bioreactors↗
PubMed2001

Consumption of fructooligosaccharides and nitrogen excretion in cats.

In a cross-over study with adult cats the effect on nitrogen (N) excretion of a diet supplemented with fructooligosaccharides (FOS) was compared with a diet supplemented with an equal amount of fructose and glucose. FOS raised N excretion with faeces by 26% (P < 0.05) and non-significantly lowered N excretion with urine by 5%. Thus, there was a shift in N excretion from urine to faeces. The amount of faecal dry matter was significantly higher (by 23.3%) when FOS was consumed.

Animals↗
PubMedDate not supplied

[Effect of ethanol adminstration in the consumption of proteins and nitrogen balance in normal subjects with normoprotein diet].

The effect of excessive alcohol intake on the protein requirements and metabolism in normal subjects has not been clearly determined. In this study we measured the nitrogen balance, the hematrocrit, the hemoglobin, the serum albumin, the cholesterol, and the plasmatic amino acids in 7 non-alcoholic subjects of 25 +/- 5 years of age. A comparison was made of a diet containing 0.8 g of protein per k of weight and 40 Kcal per k of weight administered during 11 days with a period of the same length in which the 1.400 Kcal provided during the control period by carbon hydrates was provided by ethanol (200 g). During the alcoholic period no importants changes were observed in the nitrogen balance, a tendency towards greater positivity being registered. There was a decrease in the serum albumin of 4, 69 +/- 0.31 vs 3, 90 +/- 0,32 g/100 ml and an increase in globulin 1,74 +/- 0,70 vs 2,69 +/- 0,22 g/100 ml. The results showed that in a short period of time the excessive alcohol intake in normal subjects does not increase the protein requirements in spite of a decrease in the serum albumin being observed.

Adult↗
PubMedDate not supplied

[The prognosis of endogenous nitrogen loss of the human body by the level of energy consumption].

Excretion of total nitrogen with urine and feces was studied and the value of nitrogen balance was calculated in young male volunteers under conditions of complete starvation or receiving protein-free rations of varying energy value. The data obtained were computerized and equations were derived permitting prognosis of the amount of daily excretion of endogenous nitrogen with urine and feces at different time and at any level of energy consumption.

Adult↗
PubMed1992

Low-temperature storage of bone marrow in nitrogen vapor-phase refrigerators: decreased temperature gradients with an aluminum racking system.

Large temperature gradients may exist in nitrogen vapor-phase refrigerators. Cryopreserved cells stored at higher levels may be considerably warmer than those stored closer to the liquid nitrogen reservoir. To decrease this temperature gradient, racking systems constructed of aluminum were placed in marrow storage refrigerators. The higher heat conductivity of aluminum resulted in a vapor-phase temperature gradient of only 5.9 degrees C at 22.5 inches above the liquid, as compared to the gradient of 86 degrees C seen with steel frames in a similar refrigerator. Temperature fluxes were minimal with lid opening or nitrogen filling. The thicker frame size and loss of the lowest storage level resulted in a storage capacity 63 percent of that achievable with steel frames and liquid immersion. Consumption of nitrogen was estimated to be 174 to 220 percent of the static usage in this model of refrigerator with 6 inches of nitrogen, but comparable to the consumption expected with full immersion of the racking system, regardless of frame construction. These data demonstrate the feasibility of achieving very low, stable, cryogenic temperatures in a vapor-phase refrigerator.

Aluminum↗
PubMed1988

Effect of burn and first-pass splanchnic leucine extraction on protein kinetics in rats.

The effects of burn and first-pass splanchnic leucine extraction (FPE) on protein kinetics and energy expenditure were assessed by measuring O2 consumption, CO2 production, nitrogen balance, leucine kinetics, and tissue fractional protein synthetic rates (FSR-%/day) in enterally fed rats. Anesthetized male rats (200 g) were scalded on their dorsum with boiling water (25-30% body surface area) and enterally fed isovolemic diets that provided 60 kcal/day and 2.4 g of amino acids/day for 3 days. Controls were not burned. An intravenous or intragastric infusion of L-[1-14C]leucine was used to assess protein kinetics on day 3. FPE was taken as the ratio of intragastric to intravenous plasma leucine specific activity. There was a 69% reduction in cumulative nitrogen balance (P less than 0.001) and a 17-19% increase in leucine oxidation (P less than 0.05) and total energy expenditure (P less than 0.01) in burned rats. A 15% decrease in plasma leucine clearance (P less than 0.05) was accompanied by a 20% increase in plasma [leucine] (P less than 0.01) in burned rats. Burn decreased rectus muscle FSR from 5.0 +/- 0.4 to 3.5 +/- 0.5 (P less than 0.05) and increased liver FSR from 19.0 +/- 0.5 to 39.2 +/- 3.4 (P less than 0.01). First pass extraction of dietary leucine by the splanchnic bed was 8% in controls and 26% in burned rats. Leucine kinetics corrected for FPE showed increased protein degradation with burn that was not evident without FPE correction. This hypermetabolic burn model can be useful in the design of enteral diets that optimize rates of protein synthesis and degradation.

Animals↗