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At least 37 records · Page 2Linked to original sources
PubMed2003

Spatial and temporal variabilities of nutrient limitation based on in situ experiments of nutrient enrichment bioassay.

In situ experiments of Nutrient Enrichment Bioassays (NEBs) were performed in a morphologically complex reservoir of a temperate region to identify primary limiting nutrient regulating phytoplankton productivity and determine a severeity of the nutrient limitation. Absolute nutrient contents and nutrient ratios of TN:TP and TDN:TDP in the ambient water indicated a potential limitation of phosphorus. This outcome agreed with the results of NEBs; Algal response in the P treatments, expressed as a ratio of CHLf:CHLi, showed significantly (p < 0.05) greater algal response than P + NH4-N or P + NO3-N treatments. The magnitude of the limitation, however, showed large spatial and temporal variations. The response in treatments enriched with phosphorus (P, P + NH4-N, and P + NO3-N) was greatest in the downlake zone and least in the point-source zone, while the response was greater during summer monsoon than any other seasons. Algal growth rate experiments showed that the response in treatments enriched with NO3-N and P + NO3-N never exceeded > 0.50 microg L(-1) per day and was significantly (p < 0.05) less than that in the three treatments with P (1P, 2P, and P + NH4-N), indicating a reduced response in the treatments enriched with NO3-N. The suppression of nitrate on algal growth seemed to be involved with inhibition effect of nitrogenase activity through low-nitrate uptake rate in the high nitrate-rich environment and large additions of potassium with phosphorus in spike. Regression analysis of log10-transformed CHLf:CHLi ratios against ambient nutrient contents showed that in situ algal response in the P treatments was inversely related (r = -0.77; p < 0.001) with ambient TP and positively correlated (r = 0.75; p < 0.001) with TN:TP ratios. This result suggests that in situ response depends largely on external loading of limiting nutrients.

Biological Assay↗
PubMed1991

Considerations for selecting nutrient-calculation software: evaluation of the nutrient database.

With the growing number of nutrient-calculation software packages on the market, potential users are faced with the increasingly difficult task of determining which system best meets their needs. Most published reviews of nutrient-calculation software focus on program features rather than on the quality of the nutrient database on which all calculations are based. This is unfortunate because program features are of little consequence if the nutrients calculated are not of acceptable quality. The purpose of this paper is to focus on the evaluation of the nutrient database as the foremost consideration in selecting nutrient-calculation software. Six questions that may be used as a guide for evaluating a nutrient database are presented and discussed.

Databases, Factual↗
PubMed2005

Nutrient resorption in wetland macrophytes: comparison across several regions of different nutrient status.

This study explored patterns of nutrient resorption in wetland macrophytes to test the prediction that plants from regions with a strong nutrient limitation will show higher resorption of the limiting nutrient. Nitrogen and phosphorus resorption was assessed in macrophytes from marshes of different nutrient status in tropical and temperate regions, and expressed as resorption efficiency (NRE, PRE) and proficiency (NRP, PRP). Macrophytes were grouped into three categories: Typha, graminoids and broadleaved plants. Nitrogen was less limiting than P, consequently N availability varied less than P availability, NRP and NRE were lower, and N resorption was mostly incomplete. NRP was determined more by growth form than by local conditions. The large range of soil P concentrations allowed an exploration of relationships between P availability and resorption along a wide gradient. P-limited macrophytes (N : P > 16) had significantly higher PRP and PRE. Resorption proficiency was found to be a more sensitive indicator of changes in nutrient availability than resorption efficiency. The results confirmed that resorption in wetland macrophytes depends on nutrient availability, and is higher at nutrient-limited sites. A particularly strong relationship was found between resorption indicators and P limitation expressed either as live tissue N : P or soil P.

Belize↗
PubMed2002

[Changes of crop yield and soil fertility under long-term application of fertilizer and recycled nutrients in manure on a black soil III. Soil nutrient budget].

The nutrient budget of fertilization models under different treatments was calculated using data from a field experiment over the period of 1985-1999. The results indicated that application of nitrogen fertilizer accelerated a large deficit of soil phosphorus, and the use of nitrogen and phosphorus accelerated the deficit of potassium. The experimental data demonstrated the appearance of a large area of soil deficit of phosphorus from 1970s and of potassium from 1980s in China. Nutrient recycled in farming system improved soil nutrient budget, but could not meet the nutrient requirements from high-yield crops. The use of recycled nutrients with an appropriate use of fertilizers according to the soil fertility could produce higher crop yields, balance soil nutrient budget, and not cause surplus nutrients to emit into environment.

Agriculture↗
PubMed2006

The response of nutrient assimilation and biochemical composition of Arctic seaweeds to a nutrient input in summer.

Twenty-one species of macroalgae (four Chlorophyta, eight Rhodophyta, and nine Phaeophyta) from the Kongsfjord (Norwegian Arctic) were examined for their response to nutrient enrichment (nitrate and phosphate) in the summer period. The enzymatic activities related to nutrient assimilation, external carbonic anhydrase (CAext, EC 4.2.1.1), nitrate reductase (NR, EC 1.6.6.1), and alkaline phosphatase (AP, EC 3.1.3.1), as well as the biochemical composition (total C and N, soluble carbohydrates, soluble proteins, and pigments) were measured. CAext activity was present in all species, and showed a general decrease after nutrient enrichment. Inversely, NR activity increased in most of the species examined. Changes in pigment ratios pointed to the implication of light harvesting system in the acclimation strategy. Despite enzymatic and pigmentary response, the Arctic seaweeds can be regarded as not being N-limited even in summer, as shown by the slight effect of nutrient enrichment on biochemical composition. The exception being the nitrophilic species Monostroma arcticum and, to a lesser extent, Acrosiphonia sp. For the rest of the species studied, changes in total internal C and N, soluble proteins, soluble carbohydrates, pigment content, and the internal pool of inorganic N were recorded only for particular species and no general pattern was shown. Acclimation to unexpected nutrient input seemed to ensure the maintenance of a stable biomass composition, rather than an optimized use of the newly available resource (except for the nitrophilic species). This indicates a high degree of resilience of the algal community to a disruption in the natural nutrient availability pattern.

Acclimatization↗
PubMed1971

Growth and nutrient uptake by soybean plants in nutrient solutions of graded concentrations.

Soybean plants (Glycine max L. Merr. var. Hawkeye), grown in nutrient solutions maintained at graded concentrations showed a large response in both shoot dry weight and total ion uptake. Growth rate was dependent upon nutrient concentration, even when quantity of nutrient was not limiting. Peak periods for absorption of specific ions at certain growth stages were not exhibited. Rates of ion uptake by soybeans were generally proportional to the growth rate during the period of major growth. It is suggested that a dilute nutrient solution could provide sufficient nutrients for adequate root growth prior to major shoot growth, at which time a more concentrated nutrient solution is needed.

Journal Article↗
PubMed1998

Influence of predeprivation diet nutrient density and sodium chloride content on nutrient losses and repletion in lambs.

Six crossbred lambs (32+/-2 kg) in a 6 x 6 Latin square design were used to determine the effects of predeprivation diet nutrient density and NaCl content on nutrient losses during periods of feed and water deprivation and nutrient repletion. Treatments consisted of two predeprivation dietary nutrient densities (low [LOW] and moderate [MOD]) and three NaCI intakes (0, 2, or 4 g/d) in a 2 x 3 factorial arrangement. During the 4-d predeprivation phase, lambs fed the M0D diet had greater (P < .05) K retention and lower (P < .01) Na retention than lambs fed the LOW diet. Retention of Na increased linearly (P< .01), whereas retention of K decreased linearly (P < .O01) with increasing NaCl intakes. During the 3-d deprivation phase, lambs fed the MOD diet had lower (P < .01) Na losses than lambs fed the LOW diet. Losses of Na increased linearly (P < .01), whereas losses of K decreased linearly (P < .05) with increasing NaCl intakes. During the predeprivation and deprivation phases, cumulative losses of K were greater (P < .05) and cumulative losses of Na were lower (P < .05) in lambs fed the LOW diet than in lambs fed the MOD diet. Cumulative losses of K increased linearly (P < .05) as predeprivation NaCl intake increased. Predeprivation NaCl intakes did not affect (P > .10) total retention of water, Na, or K for the overall 14-d sampling period. Predeprivation salt intakes affected Na and K losses during a simulated marketing-transport period. However, after 7 d on the realimentation diet, predeprivation diet nutrient density and NaCl intake did not affect the balance of these nutrients.

Analysis of Variance↗
PubMed2006

Setting nutrient thresholds to support an ecological assessment based on nutrient enrichment, potential primary production and undesirable disturbance.

The EU Water Framework Directive recognises that ecological status is supported by the prevailing physico-chemical conditions in each water body. This paper describes an approach to providing guidance on setting thresholds for nutrients taking account of the biological response to nutrient enrichment evident in different types of water. Indices of pressure, state and impact are used to achieve a robust nutrient (nitrogen) threshold by considering each individual index relative to a defined standard, scale or threshold. These indices include winter nitrogen concentrations relative to a predetermined reference value; the potential of the waterbody to support phytoplankton growth (estimated as primary production); and detection of an undesirable disturbance (measured as dissolved oxygen). Proposed reference values are based on a combination of historical records, offshore (limited human influence) nutrient concentrations, literature values and modelled data. Statistical confidence is based on a number of attributes, including distance of confidence limits away from a reference threshold and how well the model is populated with real data. This evidence based approach ensures that nutrient thresholds are based on knowledge of real and measurable biological responses in transitional and coastal waters.

Classification↗
PubMed1995

Food selection in anorectics and bulimics: food items, nutrient content and nutrient density.

OBJECTIVE: The food selection and nutrient intake were investigated in women with anorexia nervosa, bulimia nervosa and controls. METHODS: Dietary data was obtained by 24-hour recall, and 7-day recording among eating disordered patients, and by 3-day registration among controls. RESULTS: The intake of energy and nutrients differed from controls, as expected, while there were no differences between anorectics and bulimics in this respect, except for iron. There were only minor differences among the three groups studied with respect to nutrient density. Energy percentages of protein, fat, and carbohydrates, were similar in all groups, but a subdivision of the macronutrients into respective sources showed that bulimics had a lower relative and absolute intake of carbohydrates from bread and cereals than anorectics and controls. CONCLUSION: Eating disorder patients, despite their marginal food intake, still met the minimum requirement for most nutrients according to the Nordic Nutrient recommendations.

Adult↗
PubMed2006

Changes in carbohydrate and nutrient contents throughout a reproductive cycle indicate that phosphorus is a limiting nutrient in the epiphytic bromeliad, Werauhia sanguinolenta.

BACKGROUND AND AIMS: This study examined the physiological basis of the cost of reproduction in the epiphytic bromeliad Werauhia sanguinolenta, growing in situ in a tropical lowland forest in Panama. METHODS: Entire mature plants were sampled repeatedly over the course of 2 years, which represents the common interval between reproductive events. Due to the uncertainty concerning the appropriate currency of resource allocation to reproduction, the temporal changes of the contents of total non-structural carbohydrates (TNC) and of all major nutrient elements in different plant parts were studied (stems, green leaves, non-green leaf bases, roots and reproductive structures when present). KEY RESULTS: Although TNC varied with time in all compartments, this variation was more related to seasonal fluctuations than to reproductive status. The contents of the nutrient elements, N, P, K, Mg and S, on the other hand, showed significant differences between reproductive and non-reproductive individuals, while Ca did not change with reproductive status. Differences in nutrient contents were most pronounced in stems. Seeds were particularly enriched in P, much less so in N and the other nutrient elements. Model calculations of nutrient fluxes indicate that a plant needs about 2 years to accumulate the amount of P invested in a fruit crop, while the estimated uptake rates for N were much faster. CONCLUSIONS: Since most mature individuals of this species fruit every other year, it is hypothesized that P is the prime limiting factor for reproduction. These findings therefore add to an increasing body of evidence that P rather than N is limiting growth and reproduction in vascular epiphytes.

Biomass↗
PubMed1998

Duodenal nutrient exposure elicits nutrient-specific gut motility and vagal afferent signals in rat.

Volume and chemical characteristics of meals in the gut have been proposed to generate vagal afferent signals that mediate the negative feedback control of ingestion and gastric emptying. Furthermore, duodenal nutrients elicit changes in gastrointestinal motility that may stimulate mechanosensitive vagal afferents. The degree to which the activity of an individual vagal afferent fiber can be modified by moth mechanical and nutrient properties in the gut remains unclear. The present studies evaluated the relationships between distal antral and proximal duodenal load-sensitive vagal afferent activity and gastroduodenal motility in response to duodenal nutrient exposure in ketamine-xylazine-anesthetized rats. Duodenal carbohydrate (glucose) and amino acid (peptone) infusions (0.2 ml/min, 0.2-0.5 kcal/ml) stimulated concentration-dependent increases in 1) antroduodenal contractions and 2) antral and duodenal vagal afferent activity beyond those attributable to osmolarity alone. In addition, duodenal peptone was more effective than equicaloric glucose in eliciting this vagal activity. These data demonstrate that the proximal duodenum can discriminate its nutrient chemical contents and that gastroduodenal load-sensitive vagal afferents indirectly transduce nutrient chemical information.

Animals↗
PubMed1975

Comparison of Type A and nutrient standard menus for school lunch. I. Development of the nutrient standard method (NSM).

Methodology was developed for planning school lunch menus which meet a specific nutrient standard. The method considered nine indicator nutrients plus calories and percentage of calories coming from fat. The nutrient composition of approximately 625 school lunch menu items were calculated using Agriculture Handbook No. 8 data. All nutrient data were converted to bead units which were summed on an abacus until the meal requirements were met. Preliminary testing of the method showed it to be usable by school lunch menu planners and provided menus meeting certain minimal nutrient constraints. After the test, suggested modifications were incorporated into the method to enhance its use. The method is described and a sample week's given.

Adolescent↗
PubMed2004

Nutrient content of served food, nutrient intake and nutritional status of residents with dementia in a finnish nursing home.

PURPOSE: The aim of this study was to determine the energy and nutrient content of the served food, the actual energy and nutrient intake and the nutritional status of elderly residents in a nursing home. METHODS: The nutritional status of 23 individuals aged 69 to 89 years with dementia were assessed by Mini Nutrition Assessment -test (MNA). The nutrient content of the served food was calculated from all meals during a 14-day period. Food consumption was determined by precise weighing method. RESULTS: Of 23 residents, 20 were at risk of malnutrition and three were malnourished according to MNA. The mean energy content of the served food was 1665 kcal (7.4 MJ) per day. The amount of vitamin D in served food was too little and the amounts of vitamin E, folic acid, and fibre were somewhat lower than the recommended level. The amounts of other nutrients were sufficient or substantial. However, the true mean intake of energy in the whole group was only 1205 kcal (5.4 MJ) per day. The mean protein intake was 59 g. Intakes of vitamin D, E, and folic acid were clearly less than recommended whereas intakes of calcium, magnesium and zinc were as recommended. CONCLUSIONS: It may be possible to get enough energy and most nutrients from the served food, but many elderly nursing home residents did not eat enough. It may be helpful to individually assess, assist and monitor those residents who eat very little in a variety of ways to promote their quality of life.

Aged↗
PubMed1987

A comparative study of two microcomputer nutrient data bases with the USDA Nutrient Data Base for Standard Reference.

The results of this investigation show that when direct comparisons are made between the USDA NDB and microcomputer data bases (avoiding the confounding factors of coding judgment and the differences between older and newer USDA nutrient data), differences still can exist. N3 and FP chose to seek out alternate data when the USDA NDB provided no data for a certain nutrient. FP chose to use a large number of additional sources to supplement USDA Handbook No. 8. Although the USDA NDB was very complete for all nutrients listed except for vitamin E/total and copper, gaps are likely to continue to exist because the USDA NDB is and will be in continual revision as an increasing number of nutrients are reported for an ever-growing food supply. Therefore, in accordance with established local needs, the dietitian has the responsibility both for knowing the sources used in the microcomputer nutrient data base and for making sure that reported results are reasonable.

Computers↗
PubMed1983

Computerized nutrient data bases: I. Comparison of nutrient analysis systems.

Food composition tables now being compiled include a wide range of food items and nutrients. This trend is paralleled in the development of computer-stored nutrient data bases that are being utilized for numerous applications, such as cost-optimized menu planning, dietary record analysis, and nutritional assessment. In 1976, several participants at the National Nutrient Data Bank Conference agreed to cooperate in a comparative study to analyze a common one-day dietary record. The results of three subsequent analyses indicated that the values for nutrients varied considerably even after elimination of coding judgments relative to portion size and selection of food items. The results of the study indicated the need for an assessment methodology suitable for evaluating performance of a computerized nutrient analysis system.

Computers↗
PubMed1983

Nutrient consumption of individuals taking or not taking nutrient supplements.

Mean energy and nutrient intakes from food of 150 users or non-users of nutrient supplements were compared. Independent of supplement use, no significant differences in nutrient intakes between the two groups were observed. Some significant differences were noted in average nutrient intakes between men and women of the same age group. Fifty-three percent of the subjects reported the use of supplements, with multivitamins and ascorbic acid most often taken. Potentially toxic intakes of vitamins A, C, and E were observed for a few subjects. In general, nutrient intakes from food met the Recommended Dietary Allowances.

Adult↗
PubMed1996

Effects of nutrient HCO3- and Cl- on potential difference responses to nutrient Na+ changes in secreting and inhibited states of frog stomach.

Previously, it was found that a decrease in nutrient (serosal) Na+ decreased the transmucosal potential difference (PD) in the secreting and inhibited states of fundi of stomachs of Rana pipiens. This PD response, designated as anomalous, was explained by two different models, an electrogenic NaCl symport and an electrogenic NaHCO3 symport. To test these hypotheses, experiments were done at pH approximately 7.4 in which the PD response to a change in nutrient Na+ was compared in 25, 5, and 0 mM nutrient HCO3- solutions. In the H+ secreting state, all HCO3- concentrations gave, for a 10-fold decrease in nutrient Na+, about the same PD response (9-12 mV). The PD response was 8.5, 2.9, and 0 mV higher in the inhibited state for 25, 5, and 0 mM HCO3- , respectively. Experiments with decreasing nutrient Cl- decreased the anomalous PD response to Na+ changes, and the response became insignificant at Cl- concentrations of 20 mM or less in the secreting state. The anomalous PD response to a decrease in Na+ concentration was obtained for all Cl- concentrations (0-79 mM), becoming less with decreasing Cl- in the inhibited state. These results support a NaCl symport to explain the PD response in the secreting state and a NaHCO3 symport to explain the enhancement in the inhibited state.

Animals↗