Mean Concentrations Of Total Nitrogen Research Articles

Amino Acid and Ammonium Utilization bySaccharomyces cerevisiaeWine Yeasts From a Chemically Defined Medium

The utilization of amino acids and ammonium by nine wine strains of <i>Saccharomyces cerevisiae</i> was systematically studied in a chemically defined medium resembling the composition of grape juice. Both quantitative and qualitative differences in the utilization of assimilable nitrogen were observed. The mean concentration of total nitrogen utilized during the catabolism of 1.11 <i>M</i> (200 g/L) glucose when all amino acids were in excess was 400 mg N/L with a range of 140 mg N/L. Nitrogen utilization was influenced by the presence of air in the fermentation headspace, ammonium supplementation and initial glucose concentration. The kinetics of utilization of individual amino acids varied between strains. However, arginine, serine, glutamate, threonine, aspartate and lysine typically comprised the bulk of the nitrogen consumed. Addition of ammonium delayed and reduced the extent of accumulation of most amino acids but increased the total nitrogen consumed.

Assessment of trophic-level responses and coho salmon ( Oncorhynchus kisutch) production following nutrient treatment (1981–1986) of Bear Lake, Alaska

Bear Lake, located on the Kenai Peninsula in south-central Alaska, was treated with nutrients (mainly nitrogen) during 1981–1986 to increase coho salmon ( Oncorhynchus kisutch) smolt production through stimulating zooplankton, a known food source for juvenile coho salmon in Bear Lake. Nutrient additions increased seasonal mean total nitrogen concentrations by 145% and more than doubled the ratio of inorganic nitrogen to total phosphorus. Consistently higher seasonal mean chlorophyll a concentrations were not detected, but a significant increase in zooplankton density was detected during the period when juvenile coho salmon were absent (June–July), but not when juveniles were present (August–October) in the limnetic area of the lake. After treatment, a 25% average increase in the efficiency of Bear Lake to produce coho salmon smolt biomass was observed, and the composition of fingerlings that migrated as age-1 smolts increased by 30%. I believe the finding of no significant change in zooplankton density after nutrient treatment during August–October was due to expanded predation by juvenile coho salmon. From results of this nutrient enrichment experiment, it is clear that for a full understanding of trophic efficiency, further research is needed to integrate trophic-level dynamics with energy flow.

Regional Geology and the Chemical and Trophic State Characteristics of Florida Lakes

ABSTRACT A limnological survey of 165 Florida lakes was conducted between September 1979 and August 1980 to determine their chemical and trophic state characteristics. A wide range of limnological conditions was documented. Average lake pH values ranged from 4.1 to 9.2 and average total alkalinity concentrations ranged from 0 to 204 mg/L as calcium carbonate (CaCO3). Average specific conductance values ranged from 11 to over 5600 μS/cm at 25° C. Mean total nitrogen concentrations ranged from 0.063 to 4.6 mg/L and mean total phosphorus concentrations ranged from 3 to 834 mg/m3. Although lake trophic states ranged from oligotrophic to hypereutrophic, Florida lakes as a group can be characterized as productive, softwater lakes. Over 75 percent of the sampled lakes had total alkalinity concentrations below 40 mg/L as calcium carbonate and total hardness concentrations below 75 mg/L as calcium carbonate. Most of the sampled lakes were either mesotrophic (52 percent) or eutrophic (35 percent) because total phos...

Prediction of Emergent and Floating-Leaved Macrophyte Cover in Central Swedish Lakes

From multiple regression analysis of data from Central Swedish lakes, we suggest that the peak areal cover (hectares) of emergent vegetation is predictable from lake surface area, mean depth, and annual mean total nitrogen concentration in the lake water. The data also suggest that the percent cover of emergent macrophytes is predictable from mean depth and total nitrogen. However, the factors influencing floating-leaved macrophyte cover are not as clear.

Total Nitrogen in the Gastric Juice of Patients with Cancer and Peptic Ulcer of the Stomach

Total nitrogen, volume rate, total HCl and chloride were determined in the gastric juice of 12 patients with gastric cancer and of 17 patients with a clinical diagnosis of peptic gastric ulcer, before and after subcutaneous injection of large doses of histamine. The mean concentration of total nitrogen in the gastric juice of the patients with gastric cancer was significantly higher than in those with gastric ulcer, whereas no significant differences were found between the corresponding mean values of volume rates and concentrations and outputs of total HCl and chloride in the gastric juice of these groups of patients. It is suggested that estimation of total nitrogen concentration in the gastric juice may differentiate between cancer and peptic gastric ulcer of the stomach with a higher degree of certainty than estimation of volume rate, total HCl, or chloride.

Total Nitrogen Content of Human Duodenal Juice Before and after Intravenous Injection of Secretin

The property of secretin to alter the total nitrogen content of duodenal juice was evaluated in 27 patients. The mean concentration of total nitrogen was about 100 ml of duodenal juice before secretin stimulation and dropped to about the half after secretin. In patients with pathological values of volume or bicarbonate concentration after secretin injection, the decrease in total nitrogen concentration following stimulation was significantly less. The average value of total nitrogen concentration and that evaluated from total protein determination were 100 mg and 10-20 mg/100 ml respectively. This discrepancy may be explained by a rapid degradation of the proteins in the duodenal juice. The total nitrogen determination was inferior to the estimation of bicarbonate concentration in differentiating between a normal and pathological pancreatic function, but similar to that of volume rate and superior to the estimation of amylase activity. Before secretin stimulation a highly significant correlation was found between the concentrations of total nitrogen and those of total protein and amylase activity. After stimulation a slighter significant correlation only was found between the concentrations of total nitrogen and total protein in the first 20-minute post-secretin period.