bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of diets containing raw soya-bean flour on the vitamin B12 status of rats
Authors: Williams D. L. , Spray G. H.
Published: May 2005

1. There were statistically-significant relationships between the concentrations of vitamin B12 in the livers of rats and their urinary excretion of methylmalonic acid, both before and after the intraperitoneal injection of sodium propionate.

2. The effects of diets based on raw and heated soya-bean flour (SBF) on the growth rates, urinary excretion of methylmalonate and hepatic vitamin B12 were compared in normal and vitamin B12-depleted rats.

3. When female weanling vitamin B12-deficient rats were put on to the raw SBF diet they lost weight and became moribund after 3 weeks, even when the diet was supplemented with vitamin B12. Male adult vitamin B12-deficient rats lost weight but showed no other signs of severe vitamin B12 deficiency.

4. Stock weanling male rats were fed on raw SBF diets with or without added vitamin B12. The diets were given alone and supplemented with either methionine or a mixture of methionine, valine, threonine and tyrosine. The rats still did not grow as well as those fed on diets containing heated SBF. However, there was some evidence of increased methylmalonate excretion and lower hepatic concentrations of vitamin B12 in the rats fed on the raw SBF diets.
The vitamin B12 content of meals and items of diet
Authors: Adams J. F. , Mcewan Fiona , Wilson Alison
Published: May 2005

1. The vitamin B12 content of items of diet and of meals was measured after they had been prepared for consumption.

2. There was poor agreement between the vitamin B12 contents of meals estimated by measurements on meal homogenates and the contents estimated by calculations involving the weights and vitamin B12 contents of items.

3. The average amount of vitamin B12 absorbed per d from a hospital diet was found to be 1.7 μg.
The winged bean (Psophocarpus palustrisDesv.) in the treatment of kwashiorkor
Authors: Černý K. , Addy Hutton A.
Published: May 2005

1. A feeding trial with children suffering from kwashiorkor was conducted in which the winged bean (Psophocarpus palustrisDesv.) was used as the major source of protein in the diet.

2. Seventy-two children who had been admitted to hospital with moderate or severe kwashiorkor were included in the study. The experimental diet, prepared from a mixture of two parts of the winged beans and three parts of maize flour, enriched with a small amount of skim milk, was given to twelve children with moderate and twenty-four children with severe kwashiorkor. Equal numbers of children with similar clinical, somatometric and biochemical measurements received a control diet in which most of the protein was provided by skim milk. Both groups of children had a supplementary meal of ‘poto-poto’of negligible protein content, which supplied an extra 100–120 kJ per kg per d. The diets were introduced after the children had overcome the most acute phase of the illness during which a routine diet based on skim milk and calcium caseinate had been given. Both diets supplied 4 g protein and 435 kJ per kg body-weight and were given to the children, on the average, for 30 d.

3. The experimental diet was well accepted and tolerated, and all children made good clinical progress. The rates of gain in weight were slightly less in the experimental groups than in the children who received the control diet. Although the differences were not statistically significant, they were more marked in children whose weights were between 61 and 75% of standard (classified as second degree kwashiorkor). With both diets, mean daily weight gains were significantly higher in children with severe kwashiorkor than in those with moderate kwashiorkor.

4. The increase in total serum protein and the decrease in the amino acid ratio determined 2 weeks after admission were more marked in children given the control diet. At the end of the experimental period, however, the differences between the groups in these two measurements, as well as in values for haemoglobin concentration, protein fractions and the hydroxyproline index were no longer significant.

5. The high nutritive value and the pleasant, sweet taste, even in the raw state, are the main advantages of the winged bean. These should outweigh the disadvantage that its skin is tough and more difficult to remove than that of the soya bean.
Experimental protein-energy deficiency in rats. Ratio of serine+glycine to threonine as an index of deficiency
Authors: Salem Sohair I. , Hegazi S. M. , Morcos S. R.
Published: May 2005

1. Rats were given a low-protein (10 g/kg) diet for 16 weeks and the changes occurring in their serum amino acids were studied; during this time a full picture of protein-energy malnutrition was manifested. Groups of rats were killed at intervals of 4 weeks.

2. Food intake decreased gradually from the 4th to the 8th week, then increased slightly from the 9th to the 11th week, and then decreased again.

3. The body-weight of the rats fell progressively from the 1st week on the low-protein diet, remained stationary from the 10th to the 13th week, and then decreased again during the last 4 weeks.

4. The ratio of non-essential to essential amino acid was not correlated with the severity of protein deficiency.

5. The ratios between some individual amino acids were compared with these ratios in control rats during the 4-week periods of protein deficiency. The ratio of serine+glycine to threonine was always significantly higher in the protein-deficient than in the control rats.
Perinatal mortality, growth and survival to weaning in offspring of rats reared on diets moderately deficient in protein
Authors: Turner M. R.
Published: May 2005

1. The reproductive performance of rats reared from weaning on a moderately protein-deficient (LP) diet containing 80 g casein/kg, or on a control diet (HP) containing 250 g casein/kg has been studied. Although the rate of growth was reduced in LP animals, these rats eventually achieved the same adult weight and appearance as the controls.

2. Weight gain during the first 2 weeks of gestation was similar in the two dietary groups, but during the 3rd week HP rats gained twice as much weight as the LP animals.

3. Viable litters were produced by 78% of the HP rats mated but by only 33% of LP rats. Most of the offspring which died did so during or soon after birth; so the perinatal mortality for the offspring of LP rats was 73% compared with only 26% for control rats. After the first few days of life, the chance of survival of HP and LP offspring was similar.

4. At birth the mean body-weight of the offspring was 5.4 g for HP offspring and 4.7 g for LP offspring. However, the mean body-weight at birth of viable offspring was similar whether they were from HP or LP rats (HP 5.6 g; LP 5.3 g). At weaning, HP offspring weighed 31.2 g and LP offspring only 13.3 g.

5. When the HP diet was given to LP rats at parturition, the viable offspring achieved a weaning weight of 31.5 g, but there was no decrease in the perinatal mortality.
The effect of growth hormone on calcium metabolism in the sheep
Authors: Braithwaite G. D.
Published: May 2005

1. The effect of subcutaneous administration of bovine growth hormone on calcium metabolism of nearly mature wether sheep has been studied by a combination of a radioactive technique and a nutrient balance technique.

2. Administration of growth hormone resulted in a significant increase in the rates of absorption of Ca, accretion of Ca into bone, resorption of Ca from bone and skeletal retention of Ca, and also in the sizes of the exchangeable Ca pools.

3. Retention of phosphorus was also significantly increased.

4. These changes suggest that the effect of growth hormone was to alter the Ca metabolism of nearly mature wethers to resemble that of younger, more actively growing animals.

5. Results are consistent with the theory that oestrogens may alter Ca metabolism of wethers by increasing growth hormone production.
Occurrence and conversion of anhydrolutein into dehydroroetinol in a freshwater fish
Authors: Barua A. B. , Das R. C.
Published: May 2005

1. Lutein and anhydrolutein have been isolated from liver oils of freshly caught Sacco-branchus fossilis.

2. S. fossilis initially contained more dehydroretinol than retinol; administration of anhydrolutein to the vitamin A-depleted fish resulted in the accumulation of dehydroretinol.

3. Anhydrolutein has also been isolated from the liver oils of lutein-treated, vitamin A-depleted fish.

4. The pathway of the conversion of lutein into dehydroretinol is discussed.
The measurement of gastric transit time in obese subjects using 24Na and the effects of energy content and guar gum on gastric emptying and satiety
Authors: Wilmshurst P. , Crawley J. C. W.
Published: May 2005

1. A new method has been used to measure mean gastric transit time.

2. This method, based on the absorption of 24Na from the proximal small bowel, is simple, non-invasive and can be used at the bedside.

3. The mean transit time was increased by adding guar gum to a test meal.

4. There was a significant correlation between mean gastric emptying time and a subjective measure of satiety.
The total content of vitamin D in human milk and cow's milk
Authors: Leerbeck E. , Søndergaard H.
Published: May 2005

1. It was shown that the water-soluble fraction of cow's milk and human milk did no possess significant antirachitic activity on rats.

2. Whole cow's milk was found to contain 38 i.u. vitamin D/1. Whole human milk contained 15 i.u. vitamin D/1, of which 12 i.u. derived from the lipid fraction.

3. Thus the values found were much lower than the 204 i.u./1 in cow's milk and 950 i.u./1 in human milk given in the literature based on chemical determination of the sterol sulphate content.
A nutrition survey of children from one-parent families in Newcastle upon Tyne in 1970
Authors: Darke Sylvia J. , Disselduff Molly M. , Try G. P.
Published: May 2005

1 A 7 d total dietary record was kept in 1970 by schoolchildren from one-parent families and by a control sample matched for sex and age who were living with both parents. The children were aged, on average, 14.5 years and were from schools in Newcastle upon Tyne. Medical assessments were made within 2 weeks of the dietary study.

2. Mean daily intakes of food energy and most nutrients were significantly larger (P < 0.05) in the fatherless boys compared with the controls. There was no such difference between the corresponding two groups of girls. The quality of the diet, assessed as nutrients/MJ was similar in all four groups.

3. There was no evidence of undernutrition; a few children were considered to be obese. The findings in a period of relative affluence may serve as a baseline for subsequent dietary studies.
The induction of obesity in the rat with bipiperidyl mustard
Authors: Jagot S. A. , Webb G. P. , Rogers P. D. , Dickerson J. W. T.
Published: May 2005

Bipiperidyl mustard produced increased adiposity in the rat without excessive weight gain or hyperphagia.

The results suggest a metabolic aetiology for the obesity as opposed to a disorder of food intake regulation.
Sequential changes in plasma lipoproteins and body fat composition during polyunsaturated fat feeding in man
Authors: Shepherd J. , Stewart Jennifer M. , Clark Janice G. , Carr Kay
Published: May 2005

1. The early effects of a moderate polyunsaturated fat diet on the composition of circulating lipoproteins and adipose tissue fatty acids were measured in five healthy adults.

2. The fatty acid content and gross composition of the three major plasma lipoprotein fractions altered within 7 d of treatment. The response of depot fat was slower but did show a significant and progressive change after 14 d on the diet.

3. The efficiency of the moderate diet in changing the composition of the lipoproteins suggests that it should be equally dfective in altering their metabolic handling.
Changes in plasma concentrations of thyroxine binding prealbumin and retinol binding protein in Japanese quail after hatching
Authors: Heaf D. J. , El-Sayed M. , Glover J.
Published: May 2005

1. Male and female Japanese quail (Coturnix coturnix japonica) were reared under short daily photoperiods (8 h light–16 h dark) to inhibit sexual development with free access to food and water. Blood was sampled at frequent intervals for 13 weeks from hatching in order to monitor the developmental changes in plasma concentrations of the two proteins which are important in the transport of retinol, retinol-binding protein (RBP) and thyroxine-binding prealbumin (TBPA).

2. Measurements of body-weight, blood packed cell volume and plasma total protein concentration showed that the birds had a normal pattern of growth and haematological development. Plasma concentrations of TBPA, total immunoreactive RBP (IRBP) and holoRBP were 220, 60 and 45 μg/ml respectively in 1-d-old quail and rose to 430, 165 and 140 μg/ml at 14 d of age, which was 10 d after the corresponding change in total protein. Neither RBP nor TBPA concentrations were significantly different between the sexes during the 13 weeks, but there were minor fluctuations in concentration within relatively narrow limits.
Effects of environmental temperature on heat production, energy retention, protein and fat gain in early weaned piglets
Authors: Le Dividich J. , Vermorel M. , Noblet J. , Bouvier J. C. , Aumaitre A.
Published: May 2005

1. Six experiments each involving two groups of six piglets, were designed to study the influence of environmental temperature on heat production, energy retention and protein and fat gain in early weaned piglets. Immediately after weaning, at a mean age of 25 d, the animals were raised in two open circuit respiratory chambers. Each chamber was equipped with a totally wired cage. The piglets were paired-fed and maintained at environmental temperatures of 20, 24 or 28°. Four replicates were used for each temperature. Metabolizable energy, heat production and nitrogen balance were measured during two consecutive periods (A and B), each of 6 d duration.

2. Heat production was higher at 20° than at 24 and 28° during periods A and B. Energy retention was negative during period A, it was positive during period B and increased with temperature.

3. Protein deposition was always positive and independent of environmental temperature. The net efficiency of protein utilization was 0.77.

4. Body fat was mobilized during period A at a higher rate at 20° than 28°. During period B, fat gain increased with increase in temperature.

5. The calculated ME requirement for maintenance amounted to 411 kJ/kg body-weight0.75 per d at 28°.

6. The critical temperature of early weaned piglets raised in intensive modern housing and fed at about 90% of the ad lib. intake is close to 28° during the first 12 d after weaning.
Stimulatory effect of insulin on ruminal epithelium cell mitosis in adult sheep
Authors: Sakata T. , Hikosaka K. , Shiomura Yoko , Tamate H.
Published: May 2005

1. The rumen adapts to increased food intake by the hyperplasia of epithelial cells.

2. Volatile fatty acids (VFA) stimulate cell mitosis of sheep ruminal epithelium in vivo.

3. Since VFA generally inhibit cell proliferation in vitro insulin was proposed in this study as the possible mediator of the mitotic stimulation in vivo.

4. Infusions (6 h) of insulin (0.125 U/kg per h) plus glucose (300 mg/kg per h) (n5), and glucose alone (300 mg/kg per h) (n2) resulted in higher mitotic index of biopsied rumen epithelium (MI) during 3 or 6 to 24 h after the start of infusion, and higher plasma immunoreactive insulin (IRI) and higher plasma glucose (PG) during the infusion.

5. Insulin plus glucose infusion showed higher MI, higher IRI, and lower PG than glucose infusion.

6. Sheep infused with saline for 6 h (n1) showed no marked changes in MI, IRI, and PG.

7. Increased IRI by insulin plus glucose or glucose alone infusion was considered to stimulate cell proliferation in rumen epithelium.

8. Other possible mediations were discussed.
Utilization of low quality roughages: effects of urea and protein supplements of differing solubility on digesta flows, intake and growth rate of cattle eating oaten chaff
Authors: Redman R. G. , Kellaway R. C. , Leibholz Jane
Published: May 2005

1. Expt 1. Five 150 kg steers with ruminal, abomasal and ileal cannulas were given 3000 g oaten chaff daily plus prelleted supplement with no added nitrogen (diet A) or 50 g N/d as urea (diet B), casein (diet C), casein and formaldehyde-treated casein (HCHO-casein) (50:50 w/w; diet D) and HCHO-casein (diet E), in a 5 × 5 Latin square design. The basal diet and supplement were fed in eight equal increments at intervals of 3 h. Proportions of dry matter and organic matter digested in the stomach and whole tract were greater for diets B, C, D and E than for diet A. Total volatile fatty acid levels in the rumen and the proportion of acetic acid were lower, and the proportion of propionic acid higher on diet A than on the other diets. Rumen ammonia levels were lower on diets A, D and E than on diets B and C. N flows at the abomasum, ileum and rectum were lower on diet A than on the other diets; abomasal flows and apparent intestinal absorptions of amino acids were higher on diets D and E than on diets A, B and C. Efficiencies of bacterial protein synthesis were 15, 15, 14, 13 and 12 g bacterial N/kg OM truly digested in the stomach on diets A, B, C, D and E respectively.

2. Expt. 2. Forty 300 kg steers were fed oaten chaffad lib.plus twice the amount of the same pelleted supplements as in Expt 1. Intake of oaten chaff was 23% higher with N supplements (diets B, C, D and E) than without (diet A). Live-weight gains were 356, 798, 843, 842 and 805 g/d on diets A, B, C, D and E respectively.

3. It was concluded that efficiency of bacterial protein synthesis was not limited by the supply of peptides and amino acids in the rumen and that increases in amino acid availability in the intestines from feeding HCHO-casein did not increase food intake or live-weight gain.
Effect of zinc injection on Zn binding in cytosols of several tissues of kids
Authors: Tanabe S.
Published: May 2005

1. An experiment was conducted with goat kids to determine the effect of zinc injection on Zn binding in cytosols of several tissues of kids.

2. Following the Zn load, plasma Zn increased for 8 h then decreased. Zn injection significantly increased the Zn contents of the liver and kidney.

3. Injection of Zn into kids stimulated the production of Zn in a fraction with an apparent molecular weight of approximately 10000 in the cytosols of the liver, kidney and small intestinal mucosa. It is suggested that these fractions probably correspond to metallothioneins, Rumen papilla did not synthesize Zn-containing protein in response to an acute administration of Zn.

4. Zn injection significantly decreased the Cu content of the liver and affected the distribution of Cu in hepatic cytosol fraction, suggesting an interaction between these two elements.

5. The volume of bile collected in the gall bladder and its Zn content were markedly increased by Zn injection, suggesting that bile is one of the Zn excretion routes in kids.
Effect of methionine on the metabolic fate of liver folates in vitamin B12-deficient rats
Authors: Jågerstad Margaretha , Åkesson B. , Fehling C.
Published: May 2005

1. Hepatocytes isolated from vitamin B12-deficient and vitamin B12-supplemented rats were maintained in primary culture and were used to study the effect of methionine on the metabolism of [3H]folic acid and [5-14C]methyltetrahydrofolic acid.

2. Vitamin B12levels were reduced by approximately 75% in the hepatocytes from the deficient animals. Total folate and methyltetrahydrofolic acid concentrations were also significantly reduced.

3. There was no significanct difference in the uptake and retention of added [3H[folic acid and [5-14C]-methyltetrahydrofolic acid between the hepatocytes of the two groups. The incorporation of14C into phospholipids was reduced by approximately 60% in the vitamin B12-deficient hepatocytes (P< 0.001).

4. The addition of methionine to the culture medium doubled the uptake and retention of3H in both groups, but it did not change the amount of water-soluble14C Compounds. In the vitamin B12-deficient hepatocytes mainly methylated folate increased, whereas non-methylated folate increased in the hepatocytes of the control animals. A tenfold increase of14C incorporated into phospholipids was found in both groups after methionine was added.

5. Demethylation of methyltetrahydrofolic acid, the intracellular retention of folate and the utilization of liberated methyl groups, for example in the methylation of phospholipids, were highest in the presence of both methionine and vitamin B12suggesting an intimate co-ordination between these two substances in the regulation of folate metabolism.
Dietary protein intake and 3-methylhistidine excretion in the rat
Authors: Ward L. C. , Buttery P. J.
Published: May 2005

1. Rats were fed for 14 d on diets containing 50, 150 or 250 g/kg casein as the protein source. The daily excretion of Nt-methylhistidine (His(τMe)), a non-re-utilized amino acid, was determined.

2. His(τMe) excretion/100 g body-weight appeared to be unaffected by increasing the concentration of dietary protein from 150 to 250 g/kg. Assuming no change in the proportion of muscle in the animals these results are indicative of no change in myofibrillar protein catabolic rate. The excretion rate/100 g body-weight of the animal given 50 g/kg casein was lower than the other two treatments, especially towards the end of the 14 d treatment period. Thus at this time the myofibrillar-protein catabolic rate was lower than in the animals fed on the higher protein diet.

3. In the animals fed on the high protein diet there was a tendency for this (τMe) excretion rate/100 g body-weight to increase with age.

4. Nitrogen balance and creatinine excretion results are also presented.
Brand trust and brand extension acceptance: the relationship
Authors: Reast Jon D.
Published: May 2005

Purpose

This UK‐based research aims to build on the US‐based work of Keller and Aaker, which found a significant association between “company credibility” (via a brand's “expertise” and “trustworthiness”) and brand extension acceptance, hypothesising that brand trust, measured via two correlate dimensions, is significantly related to brand extension acceptance.

Design/methodology/approach

Discusses brand extension and various prior, validated influences on its success. Focuses on the construct of trust and develops hypotheses about the relationship of brand trust with brand extension acceptance. The hypotheses are then tested on data collected from consumers in the UK.

Findings

This paper, using 368 consumer responses to nine, real, low involvement UK product and service brands, finds support for a significant association between the variables, comparable in strength with that between media weight and brand share, and greater than that delivered by the perceived quality level of the parent brand.

Originality/value

The research findings, which develop a sparse literature in this linkage area, are of significance to marketing practitioners, since brand trust, already associated with brand equity and brand loyalty, and now with brand extension, needs to be managed and monitored with care. The paper prompts further investigation of the relationship between brand trust and brand extension acceptance in other geographic markets and with other higher involvement categories.
Tactical launch decisions: influence on innovation success/failure
Authors: Garrido‐Rubio Ana , Polo‐Redondo Yolanda
Published: May 2005

Purpose

Innovation launch strategies are usually critical for innovation success. The main objective of this work consists of analysing the influence of the tactical launch decisions on new product performance

Design/methodology/approach

Starts with a brief literature review. Then the results obtained in our study are compared with those obtained in other research. The data used in our research describes a new product launch in the Spanish agro‐food sector. The method for collecting the information was through a mailed questionnaire. Because most of response variables were categorical, and in order to verify the proposed hypotheses, cross tabulation was used. We used Pearson's chi‐squared (χ2), likelihood ratio (H2) and the adjusted residuals too.

Findings

The results propose a series of recommendations for the executives in charge of marketing new products. Specifically, suggests that it will be more likely to achieve success if, when launching a new product, skimming strategies are used, if intensive distribution is used for selling an innovation and the investment in the communication media is greater than that made by competitors. However, it is more possible to fail if the new product is marketed using an individual brand, penetration prices, push communication strategies and less expenditure on this concept than the competitors.

Research limitations/implications

The literature review suggests that some of these tactical decisions seem to be related with other launch decisions (strategic launch decisions). As a result of this, it will be interesting to perform these similar analyses for those as well as to analyse the possible links that may exist between both and their influence on the results. Future research could explore these relationships in other industrial sector or countries. Perhaps, it would be possible provide a common perspective.

Originality/value

In spite of the importance of the last phase of new product, there are few empirical works about it. This work tries to explain the transcendence of the tactical launch decisions and the influence of it on the success/failure of an innovation
Modelling density‐dependent fish shoal distributions in the laboratory and field
Authors: Hensor Ema , Couzin I. D. , James R. , Krause J.
Published: May 2005

Density‐dependent variables have long been established as an important area of ecological research, but the effects of the local density of conspecifics on grouping behaviour are less well‐studied. We compared the influence of the density of conspecifics on the shoal size distribution of killifish,Fundulus diaphanus, in the laboratory and the field. In both environments we observed an increase in shoal size and shoal number with the density of individuals present. The increase in shoal size was markedly steeper in the field than in the laboratory, but direct comparison of the two was complicated by the fact that the absolute numbers of fish present at the field site were considerably higher than those used in the laboratory trials. We developed an individual‐based model that was first used as a null model of shoal formation (defined by proximity to others) in fish with no shoaling tendency over the same range of densities used in the laboratory. Group size increased much more rapidly with increasing density in the laboratory than predicted by the null model. When we incorporated shoaling behaviour into our model, the laboratory results could be reproduced with high accuracy. However, when extrapolated to match conditions in the field, the model predicted smaller, more numerous shoals than were actually observed. We suggest this is due to heterogeneity of the field environment because fish were found to be highly aggregated in certain areas of our field site. The predictive power of laboratory studies for the field is discussed with regards to using individual‐based modelling as a tool for deriving such predictions.
Modelling occurrence and abundance of species when detection is imperfect
Authors: Royle J. Andrew , Nichols James D. , Kéry Marc
Published: May 2005

Relationships between species abundance and occupancy are of considerable interest in metapopulation biology and in macroecology. Such relationships may be described concisely using probability models that characterize variation in abundance of a species. However, estimation of the parameters of these models in most ecological problems is impaired by imperfect detection. When organisms are detected imperfectly, observed counts are biased estimates of true abundance, and this induces bias in stated occupancy or occurrence probability. In this paper we consider a class of models that enable estimation of abundance/occupancy relationships from counts of organisms that result from surveys in which detection is imperfect. Under such models, parameter estimation and inference are based on conventional likelihood methods. We provide an application of these models to geographically extensive breeding bird survey data in which alternative models of abundance are considered that include factors that influence variation in abundance and detectability. Using these models, we produce estimates of abundance and occupancy maps that honor important sources of spatial variation in avian abundance and provide clearly interpretable characterizations of abundance and occupancy adjusted for imperfect detection.
Combining genetic variation and phenotypic plasticity in tradeoff modelling
Authors: Malausa Thibaut , Guillemaud Thomas , Lapchin Laurent
Published: May 2005

Tradeoffs lead to antagonistic relationships between phenotypic traits and are thought to be determined both genetically and environmentally. We present here an allocation model that distinguishes between the genetic and environmental components of variation in resource allocation. In this model we introduced plasticity of resource allocation which was considered to be an adaptive response to environmental variations. The results show that resource allocation plasticity is a key parameter for the existence of environmental (i.e. inter environments and intra genotype) correlations and is therefore necessary to detect environment‐induced tradeoffs. We also investigated the impact of the resource allocation plasticity and other factors on genetic (i.e. inter genotypes) correlations. Our results show that resource allocation plasticity induces a masking effect of tradeoffs when studying genetic correlations and increases the masking effect of resource variation by making apparent correlations positive when negative correlations are expected. In addition, by simulating different sources of resource acquisition variation, we demonstrated that resource variation might have different effects on correlations according to the experimental design and the studied biological material. Further development of this model may be used to investigate the theoretical implications of tradeoffs in evolutionary biology and to improve design and interpretation of experimental studies.
Local and regional processes in low‐productive mountain plant communities: the roles of seed and microsite limitation in relation to grazing
Authors: Eskelinen Anu , Virtanen Risto
Published: May 2005

It is becoming widely accepted that plant community structure is determined not only by local scale factors, but that regional factors may play considerable role. The research studying the associated processes in different environments with different species assemblages is still limited. We conducted a two‐year seed sowing experiment to test whether a plant community in a low‐productive mountain snowbed is limited by seed or microsite availability and how these variables depend on natural grazing. In a factorial design, half of the plots received a mixture of seeds of fourteen species naturally occurring at the study site and above ground biomass was removed from half of the plots. These treatments were applied to plots with long term grazer exclosures and to plots accessible to grazers. Both sowing and biomass removal increased the number of seedlings, the species richness of seedlings and total species richness. The number of seedlings was higher in open plots than in exclosures in the second year. Both seedling richness and total species richness were higher in open plots. Seedling recruitment was negatively related to the amount of above ground biomass and positively to the initial species richness. These results suggest that even fairly low‐productive environments can be both seed and microsite limited and that these depend on grazing pressure. Natural grazing by mammal herbivores (e.g. lemmings and reindeer) favours species colonization and seedling emergence. Low‐productive mountain snowbeds are prone to colonization from the local species pool and even high species richness may not constrain ingression of new species.
Neonatal growth and survival of rodents in response to variation in maternal dietary nitrogen: life history strategy vs dietary niche
Authors: Parsons Jennifer L. , Hellgren Eric C. , Jorgensen Eric E. , Leslie, Jr David M.
Published: May 2005

Nitrogen (N) enrichment of terrestrial ecosystems dramatically changes ecosystem diversity and structure of plant communities. Research designed to elucidate effects of nitrogen addition on mammalian assemblages is rare. We investigated nitrogen requirements of hispid cotton rats (Sigmodon hispidus) and fulvous harvest mice (Reithrodontomys fulvescens), small mammals native to the tallgrass prairie of the southern Great Plains, USA, to better understand population responses of these species to nitrogen enrichment. We studied reproductive requirements by measuring growth of offspring under varying levels of dietary nitrogen. We predicted that dietary niche would dictate nitrogen requirements, such that the larger herbivore (S. hispidus) would have a lower dietary need for nitrogen per unit mass than the small omnivore/granivore (R. fulvescens). Reproductive output (measured as mass gain of litters and offspring) was responsive to varying nitrogen in cotton rats but not in harvest mice. Nitrogen intake that supported 50% survival of juvenile harvest mice (1.34% dietary nitrogen) also was adequate for maximum growth (1.29%). Cotton rats potentially drew on maternal nutrient stores to support litter growth at low levels of dietary nitrogen (as low as 1.08%). Overall, nitrogen requirements for maximum reproduction were greater (2.31% dietary nitrogen) for cotton rats. We conclude that life history characteristics and body size constraints rather than dietary niche explain the differential species response to variation in dietary nitrogen. Our results imply that nitrogen enrichment in old‐field succession in the southern Great Plains may lead to dominance by cotton rats and a reduction in diversity of the small‐mammal assemblage. Consumers with similar abilities to take advantage of increased environmental nitrogen may likewise dominate other ecosystems.
Habitat loss decreases predator–prey ratios in a pine‐bark beetle system
Authors: Ryall Krista L. , Fahrig Lenore
Published: May 2005

Increasing intensity of land use by humans has led to loss of natural habitats, resulting in isolation of remaining habitat fragments. Using a pine‐bark beetle ecosystem as a model, we tested the hypothesis that the ratio of abundance of predators to prey should decrease with increasing habitat loss at the landscape scale. We selected ten red pine (Pinus resinosa) sites, representing extremes of available habitat within a 2 km radius surrounding each stand. The bark beetle, Ips pini, and its coleopteran predators were sampled using baited multiple funnel traps. Effects of stand isolation were considerable; ratios of predators to prey (mean number of predators/number of prey±SE) were significantly reduced in isolated stands (0.38±0.09) as compared to those with large amounts of surrounding conifer habitat (1.63±0.41). The decline in ratio occurred both because there was: a) a lower abundance of predators (ca 0.5–0.8×) captured in isolated stands; and b) a significantly higher number of prey (ca 2.2×) captured in isolated stands. Isolation or loss of habitat, therefore, differentially affected the two trophic levels, supporting theoretical predictions. Reductions in predator abundance and, presumably, enemy‐caused mortality may lead to changes in the population dynamics of their prey species, possibly leading to increased outbreaks as habitat becomes increasingly isolated.
Macroecology of live‐bearing in fishes: latitudinal and depth range comparisons with egg‐laying relatives
Authors: Goodwin Nicholas B. , Dulvy Nicholas K. , Reynolds John D.
Published: May 2005

We examine how fishes with contrasting reproductive modes (egg‐laying versus live‐bearing) differ in geographic range size and distribution. One hypothesis based on dispersal suggests that egg‐laying taxa should occupy a wider range of latitudes than live‐bearing, whereas the opposite prediction has been derived from the idea that enhanced maternal input and a ‘safe harbor’ during development will enable live‐bearers to occupy a wider range of latitudes and depths than egg‐layers. Cross‐species analysis supports the first hypothesis for teleosts, with egg‐layers living in a wider range of latitudes than live‐bearers but at lower latitudes, across a narrower depth range and at shallow depth. However, elasmobranchs show the opposite pattern, live‐bearers having wider latitudinal ranges. Phylogenetic paired comparisons of sister egg‐laying and live‐bearing taxa confirm these contrasting patterns between teleosts and elasmobranchs. However, depth range, maximum latitude and depth do not differ with reproductive mode. Latitudinal range size increases with body size among all taxa. However, only teleosts have a positive relationship between body size and maximum latitude, depth and depth range, but this does not differ between reproductive modes. Egg‐laying elasmobranchs have low dispersal, but live‐bearers have not extended their maximum latitude or depth, despite the benefits of sheltered offspring. The differences in range size between egg‐layers and live‐bearers and the distinction between teleosts and elasmobranchs is consequence of contrasting mechanisms of dispersal and benefits of maternally buffered transport of developing offspring.
How to predict attachment potential of seeds to sheep and cattle coat from simple morphological seed traits
Authors: Römermann Christine , Tackenberg Oliver , Poschlod Peter
Published: May 2005

Dispersal is a process that determines many aspects in the life‐history of plants. Up to now, however, it is difficult to quantify. Many studies rather assess it as a categorical trait, i.e. assuming a species is dispersed by a certain vector or not. Gradual differences in the dispersal potential between species are rarely considered.

In this paper we focus on the key process of epizoochory: the attachment potential of species to animal coats. We present two simple models (GLMs) how to quantify and to predict attachment potentials to sheep wool and to cattle hair from easily measurable seed traits. To calibrate the models, we investigated the attachment potential of seeds of 130 plant species on mechanically shaken coats of sheep and cattle and measured traits describing the seeds. We found that seed mass and seed morphology were correlated with attachment potentials. For sheep wool, the combination of the logarithm of seed mass and a constant for the different seed morphology types explained 85% of the variation of attachment potentials. For cattle hair, 71% were explained. To validate the models, they were applied to 36 additional species. Predicted and experimentally measured attachment potentials were correlated with r=0.84 for sheep wool and r=0.61 for cattle wool. Thus, the attachment potential of seeds to sheep or cattle coat can be assessed for a large set of species using the described models if seed mass and seed morphology are known.
Hierarchical patterns of invertebrate assemblage structure in stony upland streams change with time and flow permanence
Authors: ROBSON B. J. , HOGAN M. , FORRESTER T.
Published: May 2005

1. Studies in several parts of the world have examined variation in univariate descriptors of macroinvertebrate assemblage structure in perennially flowing stony streams across hierarchies of spatial scale using nested analyses of variance. However, few have investigated whether this spatial variation changes with time or whether these results are representative of habitats other than riffles or of other stream types, such as intermittently flowing streams.

2. We describe patterns in taxon richness and abundance from two sets of samples from stony streams in the Otway Range and the Grampians Range, Victoria, Australia, collected using hierarchical designs. Sampling of riffles was repeated in the Otways, to determine whether spatial patterns were consistent among times. In the Grampians, spatial patterns were compared between intermittent and perennially flowing streams (stream type) by sampling pools.

3. In the Otways streams, most variation in the dependent variables occurred between sample units. Patterns of variation among the other scales (streams, segments, riffles, groups of stones) were not consistent between sampling times, suggesting that they may have little ecological significance.

4. In the Grampians streams, variation in macroinvertebrate taxon richness and abundance differed significantly between replicate streams within each stream type but not between stream types or pools. The largest source of variation in taxon richness was stream type. Little variation occurred among sample units.

5. The pattern of most variation occurring among sample units is robust both to differences in the method of sampling and different dependent variables among studies and increasingly appears to be a property of riffles in stony, perennial upland streams. High variation among sample units (residual variation) limits the explanatory power of linear models and therefore, where samples are from a single sampling time, small but significant components of variation are unlikely to represent features of assemblage structure that will be stable over time.
Responses of tropical cladocerans to a gradient of resource quality
Authors: FERRÃO FILHO ALOYSIO DA S. , DEMOTT WILLIAM R. , TESSIER ALAN J.
Published: May 2005

1. The response of three tropical cladocerans to a gradient of resource quality was compared in a series of growth bioassays using seston collected from five lakes of different depth and trophic structure in Michigan, U.S.A. To assess the food quality in terms of digestibility, assimilation experiments were performed with 32P‐labelled seston from the same lakes. Animals were also analysed for P‐content in their tissues at the end of these assays.

2. In general, assimilation efficiency was higher when animals fed on seston from shallow compared to deep lakes, and was significantly correlated with growth rates, suggesting that shallow lakes have the best food resources in terms of digestibility and P availability.

3. Results also showed that all cladoceran species responded similarly to the resource gradient, with lower growth rates in deep lakes and higher growth rates in shallow lakes, although the strength of response (sensitivity) was different among the species tested.

4. The cladoceran Moina micrura was the most sensitive species, and also displayed the highest P‐content and maximal growth rate, a pattern consistent with the growth rate hypothesis.

5. However, seston C : P ratio and growth rates in the different resources did not correlate with the animals’ P‐contents, showing an uncoupling between RNA‐phosphorus demands for growth and seston food quality.

6. In conclusion, our results support the idea that digestion resistance in algae is a major constraint to cladocerans in natural plankton communities.
Variation in spatial and temporal gradients in zooplankton spring development: the effect of climatic factors
Authors: ROMARE PIA , SCHINDLER DANIEL E. , SCHEUERELL MARK D. , SCHEUERELL JENNIFER M. , LITT ARNI H. , SHEPHERD JUDITH H.
Published: May 2005

1. We examined the temporal and spatial heterogeneity of zooplankton in lake surface waters during the spring of 3 years in Lake Washington, U.S.A., a large lake with a high production of sockeye salmon fry.

2. We show large within‐season and among‐year variation in the horizontal distribution of temperature, chlorophyll a concentration, and zooplankton in the lake. The main pattern, a delay in zooplankton population increase from the north‐ to the south‐end of the lake, recurred in each year and was persistent within each spring.

3. The delay is primarily caused by the development of a temperature gradient during spring warming, as cold mountain water enters the south end of the lake, while warm water enters the north end via a river draining a nearby lake. Climate factors, such as air temperature and precipitation during winter and spring, appear to influence the extent of the delay of zooplankton increase.

4. If the climate continues to warm, the temporal disconnection in zooplankton development between lake areas immediately influenced by cold river inflow and areas that are influenced by spring warming may increase in magnitude. Thus, the different areas of the lake may not contribute equally to fish production.
Contrasting diel activity and feeding patterns of four instars of Rhyacophila dorsalis (Trichoptera)
Authors: ELLIOTT J. M.
Published: May 2005

1. Ontogenetic shifts in prey choice and predator behaviour can affect food‐web structure. Therefore, it is important to establish if the diet and feeding activity differ between life‐stages of the same species. This hypothesis was tested for second, third, fourth and fifth larval instars of Rhyacophila dorsalis by comparing their diel activity and feeding patterns. Second to fifth instars collected from two streams were used either for gut analyses or for observations of their activity and feeding patterns in three stream tanks. Food was provided in excess; being organisms living in bryophytes on top of a large stone in each tank, augmented by different‐sized larvae of Ephemeroptera, Simuliidae and Chironomidae. As few first instars for gut analyses were found in the field, the diet of first instars reared in the laboratory was also studied.

2. Larvae for gut analyses were taken 1 h before dusk or dawn (n = 50 larvae per instar for each day or night sample). First and second instars fed on the smaller food items with no significant day‐night differences in diet. Gut contents indicated a progressive trend from feeding chiefly at night in third instars to almost exclusively at night in fifth instars. Fourth and fifth instars fed on the larger food items, whilst the diet of the third instar larvae overlapped with that of both the earlier and later instars.

3. Diel activity patterns of single larvae differed between instars but not within each instar (n = 20 larvae per instar). Second instars were active throughout the 24 h, with peaks at dusk, around midnight, dawn and around midday. A similar pattern was shown by third instars but the peak of activity at midday was less than the other three peaks. Prey were captured only during these peaks for both instars. Fourth and fifth instars were most active, and fed only, at night. They used an ambush strategy to capture more active prey at dusk and dawn (e.g. Baetis, Gammarus), and a searching strategy to capture more sedentary prey during the night (e.g. chironomids, simuliids). These experiments provided support for the hypothesis under test. If competition and/or interference occur between instars, then it could be reduced between earlier and later instars because of differences in their diet and diel pattern of feeding activity.
Greenland's shining future?
Authors: Brooks Kent
Published: May 2005

Few commodities have the charisma of diamonds and gold. In recent years both have been hitting the headlines in Greenland.