bluuebunny/crossref_metadata_2025 huggingface dataset:
Using the unique degradation ratio system (DRS) as an alternative method for feed evaluation and diet formulation: A review
Authors: YU Peiqiang
Published: March 2008

Recently obtained information on applications of the unique degradation ratio system (DRS) as an alternative method for feed evaluation and diet formulation is reviewed, in relation to optimum rumen fermentation and nutrient utilization and availability. The DRS ratio values show the balance between potentially microbial protein synthesis from rumen degradable crude protein and that potentially from the energy extracted during anaerobic fermentation in the rumen. In modeling feed evaluation and diet formulation, the degradation ratios can be used in assisting to detect effects of feed processing and optimize the composition of ruminant diets. Unfortunately, few researchers provide such crucial ratio data when they studied rumen degradation characteristics of a feed or diet mainly due to lack of knowledge of the DRS system. The emphasis of this article is on: (i) systematic introduction of the DRS system; and (ii) prediction the optimal rumen fermentation using the DRS system. The information described in this article may give better insight into the principal, computation and applications of the DRS system for feed and diet evaluation. A focus of the article is on evaluation of the DRS system as an alternative new approach to establishment of a feed evaluation system that more accurately accounts for feed digestive processes in the ruminant on a quantitative basis.
Cell wall degradation of tropical and temperate forage grasses measured by nylon bag and in vitro digestion techniques
Authors: KASUYA Natsuki , XU Qin , KOBAYASHI Yoshinao , FUKUDA Kiyoharu , ENISHI Osamu , IIYAMA Kenji , ITABASHI Hisao
Published: March 2008

Four tropical and four temperate grasses were subjected to nylon bag fiber degradation study with fistulated Holstein cattle as well as in vitro digestion with broad spectrum cellulase, and the degradability of cell wall carbohydrate and lignin for the respective forage grasses were determined. The degradability of neutral detergent fiber and acid detergent fiber for the same plant materials appeared to be similar, but that of acid detergent lignin was constantly lower. As for the plant materials used in the present study, Italian ryegrass, orchardgrass and guineagrass showed high degradability of fibers in nylon bag incubation, while setaria, cogongrass and wheat showed smaller degradability. In both nylon bag incubation and in vitro digestion experiments, the forage samples showing relatively lower degradability exhibited notably lower disappearance of xylose than that of glucose or arabinose. It was also observed that dry matter degradability correlated negatively with the initial content of esterified and/or etherified p‐coumaric acid. These results were assumed to be caused by the difference in resistance towards rumen microbial degradation due to the concentration of lignin‐carbohydrate complex.
Impact of energy and protein restriction on energy expenditure of gestation in twin‐bearing ewes
Authors: KIANI Alishir , CHWALIBOG Andre , TAUSON Anne‐Helene , NIELSEN Mette O.
Published: March 2008

This study aimed to investigate the impact of energy and protein restriction on energy expenditure of gestation (EEgest) in twin‐bearing ewes. Multiparous twin‐bearing ewes were fed either adequate (A: n = 10) or restricted to 60% of energy and protein requirements (R: n = 10) during the last 6 weeks of gestation. Whole‐body energy expenditure (EE) and retained energy (RE) were calculated from respiratory gaseous exchange combined with nitrogen balance at 7, 5 and 2 weeks prepartum. Twin lamb birth weight was lower in the R group compared to those in the A group (7.9 ± 0.31 vs 9.3 ± 0.19 kg, P < 0.01). The EEgest was lower in the R group than the A group (4.6 vs 5.9 MJ/day, SE = 0.30, P < 0.01). Between 5 and 2 weeks prepartum, EEgest contribution to the whole‐body EE significantly (P < 0.01) increased from 39% to 45% and from 34% to 40% in the A and R groups, respectively. Based on kg conceptus weight, both EEhomeorhetic (from 292 to 270 kJ/kg/day, SE = 6.2, P < 0.001) and EEconceptus (from 259 to 177 kJ/kg/day, SE = 23.8, P = 0.02) decreased between weeks 5 and 2 prepartum. The EEconceptus tended to be lower (P = 0.06) in the R group than the A group both at 5 weeks (219 vs 298 kJ/kg/day, SE = 32.8) and 2 weeks (from 138 to 217 kJ/kg/day, SE = 30.1) prepartum. In conclusion, energy and protein restriction reduced energy expenditure of gestation calculated per kg conceptus weight. The decrease may be associated with energy expenditure of conceptus growth and maintenance.
Effects of high potassium chloride supplementation on growth rate and renal function in mice
Authors: MURAI Iori , IMANISHI Satoshi , SUGIMOTO Miki , KUME Shin‐ichi
Published: March 2008

Fifty‐four mice were assigned to a control diet group or a KCl diet group to clarify the effects of KCl supplementation on growth rate, water intake and renal function in mice, and 5% of KCl was supplemented in KCl diets for 1–4 weeks. Bodyweights of KCl supplemented mice were significantly lower than those of control mice, and bodyweights of control and KCl supplemented mice at 28 days after treatment were 45.5 and 41.2 g, respectively. Feed intake was not affected by KCl supplementation, but water intake of KCl supplemented mice was significantly higher than that of control mice. Bone weights of KCl supplemented mice at 2 weeks after treatment were significantly lower than those of control mice. Serum urea nitrogen concentration at 4 weeks and serum K and Cl concentrations at 2 weeks were significantly lower in KCl supplemented mice. Histological alteration using hematoxylin–eosin and Sirius red staining was not found in the kidney of each mouse at 1, 2, and 4 weeks after treatment. These results suggest that high KCl supplementation decreases the rate of bodyweight gain and increases water intake in mice.
Comparative observation on the growth changes of the histochemical properties and collagen architecture of the Musculus puboischiofemoralis pars medialis from Silky, layer‐type and meat‐type cockerels
Authors: OSHIMA Ichiro , IWAMOTO Hisao , TABATA Shoji , ONO Yoshitaka , ISHIBASHI Akira , SHIBA Nobuya , MIYACHI Hideyuki , NISHIMURA Shotaro
Published: March 2008

Growth‐related changes in the histochemical properties and collagen architecture of the Musculus puboischiofemoralis pars medialis were compared among Silky, layer‐type, and meat‐type cockerels. Histochemical and immunohistochemical methods were employed and collagen architecture was studied using scanning electron microscopy. Total intramuscular collagen was also determined. The myofibers were categorized as type I, type IIA and a transitional form, type I‐tr. The proportion of type I‐tr myofibers diminished and these myofibers were transformed entirely into type I myofibers in meat‐type but incompletely in the others. The largest diameter of type I myofiber was found in layer‐type at 30 weeks of age. At 30 weeks of age, layer‐type birds had attained well‐developed perimysial collagen bundles while meat‐type birds had less developed bundles. The endomysial collagen network had a large mesh size at 1 week and then accumulated many collagen fibrils to form a felt‐like fabric of fibrils by 30 weeks of age. Silky birds developed the thickest endomysial collagen plates of all the breeds. From these results it appears that growth‐related changes in the histological structure of M. puboischiofemoralis pars medialis are not necessarily causally affected by the different growth rates of chicken breeds.
Estrogen receptor alpha expression in the thymus of chick embryos during late stages of embryogenesis
Authors: YONEZAWA Yasuji , SHIN Young‐ha , ABE Asaki , KONDO Yasuhiro
Published: March 2008

In the present study, we examined the presence of estrogen receptor α (ERα) in the thymus of chick embryos using two methods, reverse transcription polymerase chain reaction(RT‐PCR) with a primer set designed based on the sequence of chicken ERα–cDNA, and immunohistochemistry using anti‐ER antibody which cross‐reacts with chicken ERα. Expression of ERα mRNA was detected in the thymus of chick embryos at all stages of embryogenesis (14th to 19th day of embryogenesis) examined, as well as hen's oviducts which were used as a positive control. Scattered ERα‐positive sites were observed in the medulla of the thymus, but no sites were detected in the cortex, indicating a medulla‐limiting presence of ER‐positive sites in the chicken thymus. At high magnification under microscopic observation, ER‐positive cells were found specifically in Hassall's corpuscles or the cells in the vicinity of the Hassall's corpuscles in the medulla of the thymus. In mammalian species, Hassall's corpuscle is related to T‐cell genesis in the thymus, although the physiological significance of the component in the chicken thymus has not been reported. The results of the present study raise the possibility that estrogen plays a role in T‐cell differentiation in the thymus of chick embryos by acting on Hassall's corpuscle.
Difference in apolipoprotein E type 4 allele (APOE ɛ4) among dentate and edentulous subjects
Authors: Bergdahl Maud , Bergdahl Jan , Nyberg Lars , Nilsson Lars‐Göran
Published: March 2008

Objectives:  To evaluate the frequency of apolipoprotein (APOE) alleles and determine whether APOE type 4 allele (ɛ4) was associated with edentulousness even when certain factors were controlled.

Background:  The APOE are important in lipid homeostasis, and APOE ɛ4 has been found in many diseases and to have a negative impact on longevity. Tooth loss is more common in ill aged subjects with low income and education.

Materials and methods:  In a population‐based study involving 1860 subjects between 35 and 85 years 1321 dentate (mean age = 54; 54% women, 46% men) and 539 edentulous (mean age = 72; 62% women, 38% men) subjects were studied. Logistic regression was performed with dentate/edentulous as dependent variables and years of education, socio‐economic status, social network, stress level, handicap from birth, 23 various diseases and APOE ɛ4 as covariates. Thereafter, APOE ɛ4 frequencies were studied in 342 dentate and 336 edentulous subjects 50–85 years of age. The subjects were matched with regard to age, gender, years of education, living condition, stress level, handicap from birth and 23 various diseases.

Results:  APOE allele frequency in the total group was ɛ2 = 7.8%, ɛ3 = 76.4% and ɛ4 = 15.8%. Age, living condition, years of education and APOE ɛ4 were significant covariates in edentulous subjects (p ≤ 0.001). APOE ɛ4 in the matched groups revealed significant differences between the dentate group and the edentulous group (χ2 = 5.68; p = 0.017). There was no group effect (F(29,648) = 0.849; p < 0.696; Wilks’ lambda = 0.963). In the dentate group, the frequencies of APOE were: ɛ2 = 8.8%, ɛ3 = 77.9% and ɛ4 = 13.3%. Corresponding frequencies of APOE in the edentulous group were: ɛ2 = 6.6%, ɛ3 = 75.4% and ɛ4 = 18.0%.

Conclusion:  Despite matching both groups with regard to different background factors, the edentulous group had a higher frequency of APOE ɛ4 than the dentate group. Thus, genetic factors might contribute to greater risk in developing complex oral diseases leading to tooth loss or just be an indication that the subjects in our study carrying APOE ɛ4 are more fragile.
Ontology-Based Trajectory Simulation Framework
Authors: Durak Umut , Oğuztüzün Halit , İder S. Kemal
Published: March 2008

Trajectory simulations are tools to compute the flight path and flight parameters of munitions. We present an ontology-based object-oriented reuse infrastructure and discuss the underlying model driven development methodology. The strategic objective is to make domain knowledge and software reusable across a wide variety of trajectory simulation projects.
Knowledge Transfer: From Maintenance to Engine Design
Authors: Wong Sylvia C. , Crowder Richard M. , Wills Gary B. , Shadbolt Nigel R.
Published: March 2008

As manufacturers shift their focus from selling products to providing services, designers must therefore increasingly consider the life-cycle requirements in addition to conventional design parameters. To identify possible areas of concern, engineers must consider knowledge gained through the life cycle of a related product. However, because of the size and distributed nature of a company’s operation, engineers often do not have access to front-line maintenance data. Additionally, the large number of documents generated during the design and operation of a product makes it impractical to manually review all documents thoroughly during a design task. This paper presents a prototype knowledge-based document repository for an aeroengine manufacturer. The developed system searches and analyzes distributed document resources, and provides engineers with a summary view of the underlying knowledge. The aim is to aid engineers in creating design requirements that incorporate maintenance issues. Unlike existing document repositories and digital libraries, our approach is knowledge based, where users browse summary reports instead of following suggested links. To test the validity of our architecture, we have developed and deployed a prototype of our knowledge-based document repository. The repository has been demonstrated to and validated by the engine design community.
Design Process Modeling in Chemical Engineering
Authors: Theißen Manfred , Hai Ri , Marquardt Wolfgang
Published: March 2008

In this contribution, a methodology for modeling, improving, and implementing design processes in chemical engineering is presented. The methodology comprises a semiformal modeling language for design processes, complemented by a modeling procedure describing the efficient creation of design process models. The methodology inherits from some approaches developed in the domain of business process reengineering and workflow management, but has been extended considerably to meet the requirements imposed by the creative character of design processes. Two case studies demonstrating the successful application of the procedure for design processes in different industrial settings are discussed.
Exploitation and enrichment: the paradox of medical experimentation
Authors: Brazier M
Published: March 2008

Modern medicine is built on a long history of medical experimentation. Experiments in the past often exploited more vulnerable patients. Questionable ethics litter the history of medicine. Without such experiments, however, millions of lives would be forfeited. This paper asks whether all the “unethical” experiments of the past were unjustifiable, and do we still exploit the poorer members of the community today? It concludes by wondering if Harris is right in his advocacy of a moral duty to participate in medical research.
Allowing autonomous agents freedom
Authors: Cronin A J
Published: March 2008

Living-donor kidney transplantation is the “gold standard” treatment for many individuals with end-stage renal failure. Superior outcomes for the graft and the transplant recipient have prompted the implementation of new strategies promoting living-donor kidney transplantation, and the number of such transplants has increased considerably over recent years. Living donors are undoubtedly exposed to risk. In his editorial “underestimating the risk in living kidney donation”, Walter Glannon suggests that more data on long-term outcomes for living donors are needed to determine whether this risk is permissible and the extent to which physicians and transplant surgeons should promote living-donor kidney transplantation.1 In this paper I argue that it is not clear that medical professionals have underestimated this risk, nor is it clear that more data on long-term outcomes are needed in order to determine whether it is permissible for individual autonomous agents to expose themselves to this or, indeed, any risk. The global shortage of organs available for transplantation ultimately means that every year thousands of individuals who value their life die needlessly. This is an unacceptable loss of human life. Saving life is one of the most wonderful things an individual can do for another. Promoting any strategy that will assist in saving life and preventing human suffering within acceptable moral limits is legitimate.
Différenciation in vitro et de novo d'organes floraux directement a partir des couches minces de cellules de type epidermique de Nicotiana tabacum. Etude au niveau cellulaire
Authors: Dien Nguyen Thi , Van M. Tran Thanh
Published: March 2008

Floral organs (sepals, petals, stamens, carpels) have formed de novo and directly from explants composed of 3 to 6 layers of epidermal and subepidermal cells; these organs originated from the subepidermal layer. The first symptoms of the resumption of mitotic activity included incorporation of tritiated thymidine at the level of the subepidermal layer followed by new cell walls observed after 24 h of culturing. On the average, organogenesis from cells derived from the subepidermal layer was completed after about 10 days.This work demonstrates that the epidermal tissue can form flower buds de novo and directly. [Translated by the journal]
Classification of natural communities based on covariance and related functions
Authors: Mukkattu M. M.
Published: March 2008

The paper describes vegetation types in natural communities near London, Ontario. The methods include the use of sum-of-squares cluster analysis on data collected by systematic sampling to define vegetation types. Ranking followed by stress analysis indicates that substantial reduction of species number is possible with minimum information loss. Comparison of vegetation types by profile analysis using soil properties shows that vegetation types derived by cluster analysis may reliably indicate specific environmental conditions.
Malus tissue cultures. II. Sorbitol metabolism and carbon nutrition
Authors: Chong Calvin , Taper C. D.
Published: March 2008

Growth of callus cultures from stem explants of Malus pumila, cultivars McIntosh and Cortland, and of M. robusta No. 5, and from cotyledon explants of McIntosh was compared on standard medium with sorbitol, sucrose, glucose, and fructose, each at concentrations of 3 and 6%, and on nine other carbon sources, each at 3% concentration. Fructose was generally the most effective of the 13 carbon sources tested, although depending on concentration and callus type, sorbitol, glucose, and sucrose were as effective as fructose. Sucrose, accumulating in quantities ranging between 40 and 87% of total carbohydrate, was the predominant carbohydrate constituent found in all cultures grown on both concentrations (3 and 6%) of sorbitol, sucrose, glucose, and fructose except those grown on 6% sorbitol, which accumulated between 68 and 75% sorbitol. Cultures grown on sugars at the higher concentration accumulated between 6 and 34% sorbitol, whereas in corresponding cultures grown at the lower concentration no sorbitol was detected.
Comparative nuclear cytology of Coelastrum
Authors: Chan Kwong-Yu
Published: March 2008

The nuclear cytology of two varieties of Coelastrum proboscideum and two strains of C. microporum is described. All four Coelastrum organisms possess low chromosome numbers. Coelastrum proboscideum var. gracile Vischer has six chromosomes; C. proboscideum var. dilatatum Vischer has four; C. microporum Naegeli (strain 280) has six; and C. microporum Naegeli (strain 281) has seven. Chromatin granules are observed in C. proboscideum var. gracile Vischer, C. proboscideum var. dilatatum Vischer, and C. microporum Naegeli (281) and their condensation leads to the formation of organized chromosomes. Chromatin threads are only observed in C. microporum Naegeli (280). It is evident that the four Coelastrum organisms are quite different in their chromosomal morphology and mitotic behavior. However, at present, it is not certain whether the chromosome numbers are the haploid or diploid numbers since sexual reproduction has not been confirmed and meiotic division has not been observed.
Effect of temperature and hydrostatic pressure on algal respiration
Authors: Pope Daniel H. , Berger Leslie R.
Published: March 2008

Rates of dark respiration in Anacystis nidulans and Dunaliella tertiolecta, determined as loss of previously fixed 14CO2, were measured as a function of temperature and hydrostatic pressure. The rates of respiration in both algae decreased with decreased temperature over the range 25 to 5 °C in an approximately linear fashion and at 5 °C were only 10 to 20% of the rate at 25 °C. The rate of respiration by A. nidulans decreased with increased hydrostatic pressure. At 600 atm the rate was about 50% of that at 1 atm. Respiration by D. tertiolecta seemed to be unaffected by pressures to 600 atm. These results suggest that algal cells observed to occur in the deep oceans are potentially metabolically active at those depths; that they cannot survive for long periods of time solely through the utilization of previously stored materials; and that a heterotrophic mode of metabolism is most likely to explain their occurrence. The differential effects of temperature and pressure on various metabolic processes and growth of microalgae are also discussed.
The phenolic constituents from leaves of Manihot esculenta
Authors: Thakur M. L. , Somaroo B. H. , Grant W. F.
Published: March 2008

A total of 55 phenolic constituents was extracted with methanol – 1 % HCl at room temperature from dried leaves of cassava (Manihot esculenta Crantz). By means of thin-layer chromatographic and spectrophotometric techniques the 20 main phenolic constituents were identified as quercetin and luteolin glycosides, chlorogenic acid, esters of p-coumaric, caffeic, ferulic, and sinapic acids, and the glycosides of caffeic and ferulic acids. Benzoic acid derivatives were also confirmed. Acid and alkaline hydrolysis of the major compounds was carried out to determine their aglycones. Ultraviolet (UV) spectral data, Rf values, fluorescence in UV light, and color reactions with chromogenic spray reagents of the phenolic compounds and the aglycones are presented. The sugar residues of the major flavonoid compounds were identified as glucose.
Disassortative pollination in the distylous plant Jepsonia heterandra
Authors: Ganders Fred R.
Published: March 2008

Stigmatic pollen loads were analyzed from naturally pollinated intact and emasculated pin- and thrum-form flowers of Jepsonia heterandra. Observed pollen loads on stigmas of emasculated flowers were compared with expected loads based on random pollination. Observed pollen loads indicated that 13.2% disassortative pollination occurred in the pin form and 43.5% disassortative pollination in the thrum form. Pollen loads from intact flowers indicated that much more self pollination and geitonogamy takes place in the pin form than in the thrum form. In this species, distyly effectively promotes phenotypic disassortative pollination.It is suggested that the adaptive significance of distyly m a diallelic self-incompatible species is that the resultant disassortative pollination increases seed set in the population.
Leaf diversity in yellow birch (Betula alleghaniensis)
Authors: Dancik Bruce P. , Barnes Burton V.
Published: March 2008

Analysis of leaves from several crown positions of a single yellow birch (Betula alleghaniensis Britton) indicated that particular short-shoot leaves from the middle and lower inside crown were more uniform than those from other crown positions. The short-shoot leaves typically occur in pairs. Each pair consists of two distinctly different leaves, termed here the A and B leaves. The A leaf is consistently larger, with more veins and teeth and a more inequilateral base than the B leaf. Because of their relative uniformity, lower inside crown A leaves would be useful as "standard" leaves for among-tree and among-population comparisons. Late leaves, borne on long shoots in exposed portions of the upper crown, were smaller than the short-shoot leaves in all dimensions. Principal components and canonical variates of the short-shoot leaves from the lower and middle inside crown exhibited the most compact and least variable groupings of all of the leaf types. The first canonical variate separated the leaves of the lower and middle crown from those of the upper crown. The second canonical variate separated A and B leaves. Observations of emerging leaves indicated no systematic differences in position of the A and B leaf.
Xylary union between elongating lateral branches and the main stem in Populus deltoides
Authors: Larson Philip R. , Fisher David G.
Published: March 2008

The vasculature of elongating lateral branches was examined to determine how vessels produced in the branch unite with those produced in the main stem axis to form a continuous transport system. In a previous study it was found that differentiation of both primary and secondary xylem in a lateral bud or branch is independent of that in the main axis; i.e., xylem does not differentiate into the bud or branch from the main axis. When serial sections of the nodal region are followed downward, the bud vascular cylinder merges with that of the main axis and the adaxially situated bud traces (those nearest the stem) enter the bud gap margin first. The primary vessels of these bud traces differentiate in an oblique downward path along the margins of the bud gap, and they form radial files of primary vessels that lie adjacent to primary xylem of leaf traces in the stem. Traces situated more abaxially in the bud (those farther from the stem) contribute to other radial files of primary vessels, each of which lies progressively closer to the bud gap. Secondary xylem is initiated in the stem before it is in the branch. Consequently, the last-formed metaxylem vessels of the bud traces are continuous with secondary vessels of the stem. These latter vessels lie in the stem secondary xylem immediately external to primary xylem from the bud. Secondary xylem in the branch is initiated when foliage leaves and internodes mature. Secondary vessels formed in the branch traces are continuous with secondary vessels in the stem; these vessels are embedded in a matrix of fibers. Because cambial activity is more vigorous in the stem than in the branch, two vessels that are radially adjacent in the branch may be widely separated by fibers in the stem. The central trace of the axillant leaf enters the gap immediately below the last branch traces; at this level in the stem the leaf trace vasculature is entirely primary. The stem secondary xylem that overlies the leaf trace is continuous with that in the axillary branch.
Polarity of regeneration in excised leaves of Crassula argentea. II. Auxin transport inhibitors and auxin–cytokinin interaction
Authors: Paterson Karol E.
Published: March 2008

Two auxin transport inhibitors, triodobenzoic acid and 3,3a-dihydro-2-(p-methoxyphenyl)-8H-pyrazol(5,1-a)isoindol-8-one, inhibited the number of plantlets regenerated from leaves of Crassula argentea. This inhibition can be partially overcome with indole 3-acetic acid. The antiauxin, parachlorophenoxyisobutyric acid, reduced the amount of auxin-induced regeneration for 14 days in culture. High concentrations of isopentenyl adenine inhibited the auxin-induced regeneration response, but not the reduction in polarity of plantlet regeneration caused by exogenous auxin.
Callus formation and organogenesis by explants of six Lycopersicon species
Authors: Locy R. D.
Published: March 2008

Stem and hypocotyl explants of six Lycopersicon species, L. esculentum var. cerasiformae, L. cheesmanii, L. hirsutum, L. pimpinellifolium, L. peruvianum, and L. glandulosum, were examined for ability to form callus, adventitious shoots, and adventitious roots on media containing varying levels of indole acetic acid (IAA) and kinetin. Callus growth of L. peruvianum and L. glandulosum explants was better than that of the other species tested. Stem explants tended to form more callus than hypocotyl explants. Shoot formation by hypocotyl explants was superior to stem explants for all species and at nearly all hormone levels. Hypocotyl explants of L. peruvianum and L. glandulosum showed the highest levels of shoot formation, and L. cheesmanii and L. esculentum var. cerasiformae hypocotyl explants showed good shoot formation on media containing 3 mg/L kinetin and 0.3 or 1 mg/L indole acetic acid. No shoot formation was observed by L. hirsutum explants, and L. pimpinellifolium explants gave only a poor response. Shoot formation by stem explants was obtained only with L.. esculentum var. cerasiformae and L. glandulosum. When callus of the six species, subcultured for 63 days on a medium optimal for callus growth, was subcultured on shoot-forming media, only callus of L. peruvianum and L. glandulosum subsequently formed shoots. Callus of L. glandulosum has retained its morphogenic potential for 1 year in culture and can be used to initiate liquid suspension cultures.
A structural study of the interaction between the ectomycorrhizal fungus Pisolithus tinctorius and Pinus strobus roots
Authors: Piché Y. , Peterson R. L. , Howarth Melanie J. , Fortin J. André
Published: March 2008

Stages in ectomycorrhizal development between the fungus Pisolithus tinctorius (Pers.) Coker & Couch and short roots of Pinus strobus L. were followed in growth pouches. Short roots from preinoculation through Hartig net formation were processed for light and electron microscopy. Fungal hyphae approaching the surface of roots have Thiéry-positive substances in their modified walls and in lomasomes, indicating the possibility of extracellular polysaccharide secretion. Hyphae grow between and beneath the flattened, tannin-filled superficial root cells and subsequently into the intercellular region of the cortex. A Hartig net several hyphae wide is formed, isolating the cortical cells from each other. Plasmodesmata were not observed in these cortical cells. Middle lamella material is always present around the intercellular hyphae, suggesting limited digestion by the hyphae. Cortical cell cytoplasm becomes necrotic in regions of mature Hartig net formation.
Lignocellulose degradation by Fusarium species
Authors: Sutherland John B. , Pometto III Anthony L. , Crawford Don L.
Published: March 2008

Eighteen strains of fungi in the genus Fusarium, including varieties of F. episphaeria, F. lateritium, F. moniliforme, F. nivale, F. oxysporum, F. rigidiusculum, F. roseum, F. solani, and F. tricinctum, slowly degraded lignocelluloses from blue spruce (Picea pungens) and wheat (Triticum aestivum). When grown with [lignin-14C]lignocellulose from blue spruce, 15 of the Fusarium strains converted 2.2 to 4.3% of the [14C]lignin in 60 days to 14CO2 and 3.9 to 8.4% to labeled water-soluble products. When grown with unlabeled lignocellulose from wheat straw, the strains caused total weight losses in 60 days of 7 to 25%, acid-insoluble (Klason) lignin losses of 2 to 17%, and carbohydrate losses of 3 to 33%. Crude protein contents of degraded wheat-straw lignocellulose samples were 3.2 to 5.1%. Among the aromatic degradation products from wheat-straw lignocellulose degraded by different strains, as shown by gas chromatography, were p-coumaric acid, vanillic acid, vanillin, syringaldehyde, and p-hydroxybenzaldehyde.
Silicon distribution in the nodal roots of the grass Miscanthus sacchariflorus
Authors: Sangster A. G.
Published: March 2008

Nodal roots of field-grown specimens of the grass Miscanthus sacchariflorus (Maxim.) Hackel were prepared for anatomical study and Si microanalysis using light microscopy, scanning electron microscopy, and energy-dispersive X-ray microprobe analysis. Si was confined to the inner tangential wall of tertiary-state endodermal cells and occurred as large nodular silica aggregates in close proximity to large pit canals. The silicon distributional pattern appears consistent with that determined for roots of other genera of the tribe Andropogoneae, supporting the concepts that such deposition is predictable as to its perivascular location and also that it might be determined by phylogenetic affinities.
Light and electron microscopy of embryo development in an annual × perennial Medicago species cross
Authors: Sangduen N. , Kreitner G. L. , Sorensen E. L.
Published: March 2008

Using light and transmission electron microscopy, we studied embryo development from 3 to 14 days after pollination in an interspecific Medicago cross (perennial M. sativa L., 2n = 4x = 32 × annual M. scutellata (L.) Mill, 2n = 4x = 32) to determine factors contributing to abortion in wide crosses. An intraspecific M. sativa cross and an M. sativa self-mating were used for control embryos. Nucellus and integumentary tapetum at the base of the embryo sac appear to be important sources of nutrition during the first 2 weeks of embryo development. Micrographic evidence supports the conclusions that maternal and embryonic tissue of interspecific ovules fail to carry out a timely sequence of metabolism involving lipid, starch, and nucellar crystals. Delayed breakdown of starch and lipid in the integumentary tapetum and nucellus is a probable factor in reduced development of coenocytic endosperm. At the late heart stage of embryo development, relative inactivity of dictyosomes and endoplasmic reticulum in hybrid ovules suggests failure of nutrient metabolism and transport in all nutritive tissue including the nucellus, integumentary tapetum, endosperm, and suspensor of the embryo. Early embryo development in Medicago appears to be a complex phenomenon requiring a high degree of coordination between anabolism and catabolism in both maternal and embryonic tissue.
Resource allocation and reproductive and life-history strategies in widespread populations of Rumex crispus
Authors: Hume L. , Cavers P. B.
Published: March 2008

Genetically based differences among widespread populations of Rumex crispus L. from 10 localities in eastern North America and 1 in Bangor, Wales, were examined. Plants from all populations allocated the same proportions of resources to reproductive and vegetative plant parts when grown under cultivation in a common environment. Within these two major components, resources were allocated in different ways, adapting local populations to their respective environments. For example, plants from the warmest localities produced relatively small numbers of large achenes. Also, large achenes were produced from localities with the least precipitation during their dry season. Plants from populations at New Orleans, LA, College Station, TX, and Halifax, N.S., had shorter life-spans than those from other localities sampled. For the New Orleans population this was at least partly due to plants lacking the rigorous vernalization requirements of the more northerly populations. These individuals bolted in the fall and were winter-killed.
A statistical modeling method for estimating mortality and abundance of spawning salmon from a time series of counts
Authors: Szerlong R Glenn , Rundio David E
Published: March 2008

We present a statistical modeling method for estimating mortality and abundance of spawning salmon from time-series counts that eliminates the need for separate information about mortality. We model arrival and mortality using differential equations, where mortality can be constant or changing linearly, and estimate mortality and abundance from counts using maximum likelihood when multiple estimates of detection rate are available. We also develop an approximate likelihood to estimate mortality and abundance when only a single value for detection rate is available or to estimate only mortality when detection rates are entirely unknown. We demonstrate our approach using counts of coho salmon (Oncorhynchus kisutch) where mortality, abundance, and detection were determined from tagging at a weir. Our model for nonconstant mortality produced mortality estimates that closely matched the empirical data and were robust to variation in other parameters. It also provided a better fit to the stream counts and a closer abundance estimate to the weir count than the constant mortality model. Monte Carlo simulations indicated that the approximate likelihood provided reasonable estimates of mortality over most of the ranges of parameters explored, particularly under the nonconstant mortality model, and produced relatively unbiased abundance estimates using a single value for detection.
Retention, breakdown, and biological utilisation of deciduous tree leaves in an estuarine tidal flat of southwestern British Columbia, Canada
Authors: Sakamaki Takashi , Richardson John S
Published: March 2008

In an estuarine mudflat connected to a mountainous stream, coarse leaf material from deciduous trees was examined for its utilisation by invertebrates, retention, and breakdown rate. Leaves from the stream were deposited in the upper intertidal parts near the stream mouth. Their standing stocks were high in fall (~23.8 g AFDM·m–2) and mostly disappeared by spring. Breakdown rates of red alder leaf packs were higher at subtidal and lower intertidal stations (k = 0.013–0.027·day–1) than at stream channel and upper intertidal stations (k = 0.006–0.009·day–1). Longer contact of leaves with relatively warmer seawater may have enhanced leaf breakdown by microbial activities. In the upper intertidal stations, the decrease in the amount of deposited leaves from fall to spring (k = 0.023–0.039·day–1) was faster than leaf breakdown in the leaf packs, thus physical export was probably significant in the decrease in deposited leaves. Meanwhile, amphipods dominated the invertebrates colonising leaf packs. The invertebrate densities did not significantly differ between natural and polyester leaf packs, suggesting contribution of leaves as a microhabitat rather than a food source. The carbon and nitrogen stable isotope signatures of amphipods indicated that benthic microalgae were their primary food source regardless of natural or artificial leaf packs.
An age-structured model with leading management parameters, incorporating age-specific selectivity and maturity
Authors: Forrest Robyn E , Martell Steven J.D. , Melnychuk Michael C , Walters Carl J
Published: March 2008

Previous authors have shown analytically that the optimal equilibrium harvest rate (UMSY) for an iteroparous fish stock is a function of the slope of the stock-recruitment curve at low stock size (α) and that UMSY can therefore be considered a direct measure of stock productivity. As such, it can be used as a leading parameter in stock assessment models and directly estimated using Bayesian or similar techniques. Here we present an alternative method for deriving α from UMSY that incorporates age-specific selectivity and fecundity, avoiding assumptions of knife-edged recruitment and maturity. We present an age-structured model with two fisheries reference points (UMSY and maximum sustainable yield, MSY) as its leading parameters. We show equilibrium properties of the model, chiefly in terms of its ability to show relationships between life history traits, density dependence, and UMSY. We also demonstrate a simple Bayesian estimation routine to illustrate estimation of UMSY and MSY directly from data. We compare our results to those from a structurally identical model with leading biological parameters. Using models with leading management parameters can improve communicability of results to managers.
Predictive modeling and spatial mapping of fish distributions in small streams of the Canadian Rocky Mountain foothills
Authors: McCleary Richard J , Hassan Marwan A
Published: March 2008

We developed an automated procedure for modeling spatial distribution of fish occurrence using logistic regression models and geographic information system (GIS) tools. Predictors were measured from a digital elevation model (DEM) and stream layers. We evaluated the accuracy of GIS measures of reach slope through a comparison with field measures. Resource selection function models were used to explain presence-absence of bull trout (Salvelinus confluentus), rainbow trout, (Oncorhynchus mykiss), nonnative brook trout (Salvelinus fontinalis), and all fishes. Our models were extrapolated based on low, medium, and high levels of probability to produce reach-scale maps across 12 000 km2. We attempted to improve models by adding land-use variables; however, the terrain best suited to road building and harvest also contained the habitat selected by rainbow trout, whereas bull trout generally selected terrain too steep for land use. These confounding factors emphasize the need for process-based investigations in addition to correlative approaches to identify habitat requirements. This automated method provides a rapid evaluation of fish habitat across remote areas useful for salmonid conservation and research planning.
Population genetic structure of the snow crab (Chionoecetes opilio) at the Northwest Atlantic scale
Authors: Puebla Oscar , Sévigny Jean-Marie , Sainte-Marie Bernard , Brêthes Jean-Claude , Burmeister AnnDorte , Dawe Earl G , Moriyasu Mikio
Published: March 2008

Marine species with planktonic larval durations of several months (teleplanic larvae) can potentially maintain demographic connectivity across large geographical distances. This perspective has important fundamental and applied implications, notably for the understanding of evolutionary and ecological processes in the marine realm, the implementation of marine protected areas, and fisheries management. Here we present, at the scale of the Northwest Atlantic, a spatial analysis of snow crab (Chionoecetes opilio, Majoidea) population genetic structure, a species that has a planktonic larval phase of 3 to 5 months. Eight microsatellite markers analysed on 847 C. opilio samples from 13 locations revealed an absence of significant genetic structure along the west coast of Greenland and within Atlantic Canada from southern Labrador to Nova Scotia. These results are consistent with a scenario of extensive demographic connectivity among C. opilio populations and have implications for the management of this species, which supports one of the most important Canadian and Greenlandic fisheries in terms of economic value. A genetic break is nevertheless identified between Greenland and Atlantic Canada, showing that genetic structure can develop within seas (the Labrador Sea in this case) despite the occurrence of very long planktonic larval stages.
Invasive zebra mussels (Dreissena polymorpha) increase cyanobacterial toxin concentrations in low-nutrient lakes
Authors: Knoll Lesley B , Sarnelle Orlando , Hamilton Stephen K , Kissman Carrie E.H. , Wilson Alan E , Rose Joan B , Morgan Mechelle R
Published: March 2008

We investigated whether concentrations of the cyanobacterial toxin microcystin were positively associated with Dreissena polymorpha invasion by conducting surveys of 39 inland lakes in southern Michigan with low to moderate total phosphorus concentrations (≤20 µg·L–1). Lakes with D. polymorpha had 3.3 times higher microcystin concentrations and 3.6 times higher biomass of Microcystis aeruginosa (a major producer of microcystin) than comparable lakes without D. polymorpha. In contrast, the biomass of Anabaena spp. (another potential producer of microcystin) was 4.6 times higher in lakes without D. polymorpha. We also conducted a large-scale enclosure manipulation of D. polymorpha density in Gull Lake, a low-nutrient lake containing D. polymorpha. The experiment revealed a positive effect of D. polymorpha on microcystin concentrations and M. aeruginosa biomass. The congruence between survey and experimental results provides strong evidence that D. polymorpha invasion causes an increase in toxin concentrations in lakes with low to moderate nutrients. An increase in M. aeruginosa biomass may negatively impact food webs and public health because microcystins are known to be toxic to aquatic and terrestrial organisms.
Pronounced long-term juvenation in the spawning stock of Arcto-Norwegian cod (Gadus morhua) and possible consequences for recruitment
Authors: Ottersen Geir
Published: March 2008

The oldest and largest individuals are disappearing from many fish stocks worldwide as a result of overexploitation. This has been suggested to impair recruitment through decreasing the reproductive capacity of the spawners and increasing the mortality rate of the offspring. By using a time series on spawners biomass by age class for Arcto-Norwegian cod (Gadus morhua) from 1913–2004, I have documented pronounced changes in the spawning stock, including a trend towards younger fish, a less diverse distribution across ages, and a declining proportion of repeat spawners. Despite the total spawning stock biomass (SSB) being at similar levels now as in 1933, the mean age in the SSB has declined from 10–12.5 years to 7–8 years during the study period, and the percentage of fish of age 10 or above in the SSB has decreased from ~97% to ~10%. Contrary to earlier theoretical and experimental studies, no clear link between age structure and recruitment was found here. Recruitment to the Arcto-Norwegian cod stock may thus be more robust towards spawner juvenation than expected, possibly because of strong recruitment compensation.
Comment on “Rate of species introductions in the Great Lakes via ships’ ballast water and sediments”
Authors: Reid Janet W , Hudson Patrick L
Published: March 2008

The four species of freshwater copepod crustaceans found in ballast water or sediments in ships and characterized as “nonindigenous” to the Laurentian Great Lakes region by Drake and Lodge (Can. J. Fish. Aquat. Sci. 64: 530–538 (2007)) are all widespread, North American natives. Drake and Lodge’s use of these native species to estimate the size of the “source pool” of the richness of potential invasive species resulted in an overestimation of its size. We list the fresh- and brackish-water species of copepods found in or on ships in the Great Lakes and discuss taxonomic and other questions pertaining to some of them. We suggest that Skistodiaptomus pallidus, Cyclops strenuus, Salmincola lotae, Nitokra incerta, and Onychocamptus mohammed be removed from the current list of nonindigenous copepod and branchiuran species established in the Great Lakes system, leaving seven species: Eurytemora affinis, Megacyclops viridis, Neoergasilus japonicus, Heteropsyllus nunni, Nitokra hibernica, Schizopera borutzkyi, and Argulus japonicus.
Fast-ion-beam laser-induced-fluorescence measurements of branching fractions and oscillator strengths in Nd II
Authors: Li R , Rehse S J , Scholl T J , Sharikova A , Chatelain R , Holt R A , Rosner S D
Published: March 2008

We measured the spontaneous-emission branching fractions of 46 levels in Nd II, selectively populated via single-frequency laser excitation of a 10 keV ion beam. The levels studied had term energies up to 29 955 cm–1, and decay branches with spontaneous emission in the range 372–850 nm were detected. The experimental accuracy for branching fractions over 0.1 was ~7%. We used these branching fractions along with our previously determined radiative lifetimes to infer transition probabilities and oscillator strengths for 430 transitions, which are useful for stellar abundance determinations.

PACS Nos.: 32.70Cs, 95.30Ky