bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal patterns of photosynthesis and respiration of red spruce saplings from two elevations in declining southern Appalachian stands
Authors: McLaughlin S. B. , Andersen C. P. , Edwards N. T. , Roy W. K. , Layton P. A.
Published: July 2008

Exploratory studies were initiated at two high-elevation red spruce (Picearubens Sarg.) stands in the Great Smoky Mountains of western North Carolina to document the magnitude and physiological basis of differences in tree growth at the two sites. Increment core data indicate that conditions have become relatively less favorable for mature trees at the upper site during the past 20 years and that annual height growth of sapling trees has been 40% less at that site compared with a similar site at an elevation 215 m lower. Seasonal measurements of net photosynthesis and dark respiration rates of saplings indicated that differences in sapling growth rates at the upper site were associated with increases in dark respiration and less favorable net photosynthesis:dark respiration ratios. Basal diameter increment was most closely associated with differences in current net photosynthesis rates among trees at the upper site, whereas height and diameter growth of the upper canopy related most closely to the net photosynthesis rate among lower-elevation trees. Reduced foliar calcium and magnesium, reduced foliar chlorophyll, increased foliar aluminum, and low ratios of calcium:aluminum were found at the upper site. Tissue and soil aluminum levels that are in the range of those associated with aluminum toxicity to red spruce provide a preliminary indication that current high atmospheric inputs of the strong anions SO4 and NO3 to acidic soils may be adversely affecting growth and physiology of trees at the high-elevation site.
Influences of light intensity on weed-induced stresses of tree seedlings
Authors: Kolb T. E. , Bowersox T. W. , McCormick L. H.
Published: July 2008

Growth of northern red oak (Quercusrubra L.), white ash (Fraxinusamericana L.), and white pine (Pinusstrobus L.) seedlings was evaluated for 2 years after germination in 12 environments that consisted of four levels of herbaceous interference (fern, fern free, grass, grass free) crossed with three levels of light intensity (100, 45, and 20% full sun), at two clear-cuts in central Pennsylvania. Grass and fern interference reduced soil moisture content and reduced height or diameter growth of all species. Shading ameliorated soil moisture, reduced herbaceous growth, generally reduced growth of all tree species in interference-free environments, and had no effect on growth of any tree species in fern and grass environments. Reduction in growth due to herbaceous interference was lower for northern red oak and white pine than for white ash, while shading had similar effects on growth of all species. Results suggest that stresses induced by shading alone have little short-term effect on the establishment of these species under conditions of heavy herbaceous interference.
Effects of shoot pruning on stem growth, needle biomass, and dynamics of carbohydrates and nitrogen in Scots pine as related to season and tree age
Authors: Långström B. , Tenow O. , Ericsson A. , Hellqvist C. , Larsson S.
Published: July 2008

In a field experiment in central Sweden, current shoots representing one-fifth of the needle biomass were removed from Scots pine (Pinussylvestris L.) by hand pruning young and old trees and by inducing Tomicuspiniperda (L.) (Coleoptera: Scolytidae) attacks on caged young trees. Branches in the uppermost whorls were pruned in later summer, early summer, or both. Starch and nitrogen concentrations in needles were monitored for two growing seasons. After four seasons the trees were felled and effects on growth were recorded. Starch and nitrogen concentrations in needles of pruned branches decreased and increased, respectively, compared with the controls. In old trees, but not in young ones, the raised nitrogen level persisted for 3 years after pruning. Starch and nitrogen concentrations in unpruned branches of pruned whorls did not change compared with the control until these branches became pruned, i.e., each branch acted as a semiautonomous integrated physiological unit. At felling, pruned trees were short of a portion of needle biomass equal to that removed, while at the same time, the needle biomass grown out above the pruned whorls was larger than the corresponding part of the controls. Stem volume losses in old hand-pruned trees were larger than and lasted longer than in young ones and were not yet completed four growing seasons after treatment. In a stepwise linear regression analysis, final needle biomass explained most of the total variation in volume growth of young hand-pruned trees, whereas for old trees, intertree competition was more important. Responses of beetle-pruned trees were similar to those of young hand-pruned trees. Differences in response to pruning and defoliation and in recovery between young and old trees are discussed in terms of source and sink theory and of compensatory mechanisms and carbohydrate limitation, respectively.
Application and comparison of spatial models in analyzing tree-genetics field trials
Authors: Magnussen Steen
Published: July 2008

Tree height of jack pine full-sib families, originating from all possible combinations of three parental provenances and growing on three sites, was analyzed with 1 classical model and 11 nearest-neighbour spatial process models. Extension of the classical linear model with spatial interaction terms was deemed necessary in light of significant neighbourhood correlations among effect-free observations (residuals) on two of the three sites. The strength and extent of spatial and temporal correlations are demonstrated in both visual and tabular form. Only 4 of the 11 spatial models provided a substantial reduction (5–20%) in the significant difference between two estimates of full-sib family tree height. Spatial adjustments averaged 1–3% at the family level, with few families adjusted by more than 10%. The cumulative (temporal) effect of spatial covariance was demonstrated in rank correlations between adjusted and observed family means. No simple trends were obtained when adjusted variance components and heritabilities were compared with their unadjusted counter-parts, but most models tended to deflate genetic effects and reduce heritabilities. It is concluded that although spatial analyses provide an attractive tool for the experimenter, the lack of a cause and effect hypothesis in forest genetic trials necessitates model searching without the guarantee of true treatment effects. Spatial analysis provides good indicators of the need to collect additional site information for more powerful analyses. Careful planning and intensive site preparation may greatly reduce spatial covariances and the need for spatial analyses.
Effects of fire on the vegetation of Siberian taiga predominated by Larixdahurica
Authors: Uemura Shigeru , Tsuda Satoshi , Hasegawa Sakae
Published: July 2008

In the summer of 1988, a vegetation survey of the Siberian taiga was conducted in a discontinuous permafrost zone of northern China where a destructive fire had occurred in the spring of 1987. The dominant forest cover of this area was larch, with spruce forests occurring in wet valleys and pine forests on steep, dry slopes. The vertical structure of forests showed that the spruce forests were preceded by larch forests; however, most of the larch forests were self-renewable probably because their habitats were too dry for spruce trees to compete. In larch forests, the 1987 fire seriously damaged perennial herbs; in spruce forests, however, most of the herbaceous plants were protected by wet conditions of their habitats, except feather mosses, which could not survive in the habitat opened by fire. Many plants of the burnt habitats recovered vegetatively; in particular, the burnt stems of birch trees frequently sprouted many shoots and consequently appeared to be contributing to the rapid reestablishment of larch, which is generally preceded by birch trees in ecological succession. Pine forests were not self-renewable; however, they seemed independent of the normal course of succession by dominating dry habitats where their competitors were not successful.
Frost hardiness, root growth capacity, and field performance relationships in interior spruce, lodgepole pine, Douglas-fir, and western hemlock seedlings
Authors: Simpson David G.
Published: July 2008

Interior spruce (Piceaglaucaengelmannii complex), lodgepole pine (Pinuscontorta Dougl.), Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), and western hemlock (Tsugaheterophylla (Raf.) Sarg.) were grown from seed for 20 weeks in containers, with 18-h photoperiods. Fortnightly, over a 12-week acclimation period (September 7 – December 1) outdoors at Vernon, B.C., samples were taken for (i) foliage frost hardiness measurement, (ii) poststorage root growth capacity, and (iii) outplanting on forest sites. In all species, frost hardiness and root growth capacity increased with weeks of acclimation. Frost hardiness and root growth capacity were correlated with each other in western hemlock, lodgepole pine, and Douglas-fir, and with field performance (survival or growth) in interior spruce, lodgepole pine, and Douglas-fir.
Response of thinned, immature lodgepole pine to nitrogen and boron fertilization
Authors: Brockley R. P.
Published: July 2008

A study was undertaken to investigate the effects of nitrogen and boron, applied singly and in combination, on the growth of young, thinned lodgepole pine in the interior of British Columbia. Results indicate that subacute boron deficiencies without visible growth disturbance symptoms, may reduce the nitrogen fertilization response potential of lodgepole pine. Combined nitrogen and boron application significantly improved the 3-year mean height and volume increment over that obtained with nitrogen alone. Relatively small boron additions (i.e., 1.5 and 3.0 kg boron•ha−1) to the soil surface elevated foliar boron concentrations and maintained them throughout the 3-year study period. No toxic effects of boron application on foliage were observed. Both 1st-year fascicle weight response and 2nd-year branch elongation proved to be reliable indicators of subsequent stem volume response. The slightly larger stem growth response obtained with a complete fertilizer treatment, when combined with needle weight and foliar analysis data, indicates that nitrogen and nitrogen plus boron treatments may have induced a marginal sulphur deficiency. Because boron deficiency symptoms can develop rapidly following an interruption in boron uptake, and because top dieback can have such an adverse effect on stem quality and value, it is recommended that boron be added to nitrogenous fertilizer when undertaking aerial fertilization projects in lodgepole pine forests where average foliar boron concentrations are below 15 ppm.
Prediction of frost hardiness in seedlings of Scots pine (Pinussylvestris) using multivariate analysis of chlorophyll a fluorescence and luminescence kinetics
Authors: Sundblad Lars-Göran , Sjöström Michael , Malmberg Gunilla , Öquist Gunnar
Published: July 2008

Seedlings of Scots pine (Pinussylvestris L.) were artificially frost hardened under controlled conditions. To follow the development of hardiness, the frost killing temperature was determined. Four levels of hardiness were defined during the course of frost hardening. After adaptation of the seedlings to dark conditions at room temperature, fluorescence induction and far red induced luminescence decay kinetics were recorded for seedlings of the four defined levels of hardiness. The induction curve of fluorescence and the decay curve of luminescence were digitized for 110 time intervals, and the values were used in a multivariate partial least squares analysis to evaluate the potential of luminescence and fluorescence as predictive probes for cold hardiness. The results showed that both fluorescence induction and luminescence decay kinetics contain information allowing the prediction of frost hardiness of artificially cold-hardened seedlings of Scots pine.
Effect of temperature on needle anatomy and transpiration of Piceamariana after bud initiation
Authors: Vanhinsberg N. B. , Colombo S. J.
Published: July 2008

Six-month-old black spruce (Piceamariana (Mill.) B.S.P.) container seedlings were placed in either a cool (18 ± 4: 6 ± 4 °C, light:dark) or a warm (26 ± 3: 18 ± 2 °C, light:dark) hardening regime for 12 weeks after bud initiation to assess the effects of temperature on needle maturation and transpiration. Stomatal transpiration was greater in warm-hardened seedlings than in cool-hardened seedlings. Cuticular transpiration was found to be greater in cool-hardened excised shoots than in warm-hardened shoots. Needle cuticle thickness increased in seedlings exposed to both warm and cool temperatures, however, cuticular growth after bud initiation was greater in the warm-hardening regime.
Overland flow and soil movement from forests in Kumaun Himalaya
Authors: Loshah D. C. , Upadhyay V. P. , Singh R. P. , Singh J. S.
Published: July 2008

Overland flow and soil movement were measured on small plots of three forest types in the Kumaun Himalaya. Average seasonal (June through September) overland flow (measured over 2 years) was 0.49% of the seasonal rainfall (1967 mm) and was always less than 1% of each rain event (there was less than 0.1% difference among forest types). Seasonal soil movement ranged from 2.3 to 3.2 g•m−2 among forest types and averaged 2.6 g•m−2. Both overland flow and soil movement were significantly different between months, being positively correlated with amount of rainfall. Sediment concentration of runoff water did not vary among months by more than 0.1 g•L−1. The study indicates that steep, forested slopes are not an important sediment source in Kumaun Himalaya.
The mycorrhizal and nodulation status of container-grown trees and shrubs reared in commercial nurseries
Authors: Danielson R. M. , Visser S.
Published: July 2008

To guide in deciding whether artificial inoculation of container-grown woody seedlings used for reclamation purposes in Alberta might be beneficial, a survey was made of seven nurseries to determine the symbiotic status of plants ready for outplanting. Eight species of woody shrubs were rarely vesicular-arbuscular mycorrhizal if less than 1 year old and were erratically mycorrhizal after 1 to 2 years nursery residence time. Actinorhizal shrubs (Elaeagnuscommutata Bernh. ex Rydb. and Shepherdia spp.) did not become nodulated in the 1st year, and planting stock generally lacked N2-fixing ability. The mycorrhizal status of pines (Pinusbanksiana Lamb, and Pinuscontorta Dougl.) and white spruce (Piceaglauca (Moench) Voss) seedlings ranged from mycorrhizal-free to complete mycorrhization. A majority of the mycorrhizae were formed by Thelephoraterrestris Ehrh.:Fr., E-strain (Complexipes), and Myceliumradicisatrovirens Melin. Amphinemabyssoides (Fr.) J. Erikss. formed a large proportion of the mycorrhizae on white spruce, which were held in nurseries for over 1 year. A stipitate polypore, Coltricia sp., is reported as a mycorrhizal associate of nursery stock for the first time.
A methodology for estimating canopy disturbance frequency and intensity in dense temperate forests
Authors: Lorimer Craig G. , Frelich Lee E.
Published: July 2008

not available
Canopy gaps in forest ecosystems: an introduction
Authors: Denslow Julie S. , Spies Thomas
Published: July 2008

not available
Light regimes beneath closed canopies and tree-fall gaps in temperate and tropical forests
Authors: Canham Charles D. , Denslow Julie S. , Platt William J. , Runkle James R. , Spies Tom A. , White Peter S.
Published: July 2008

Light regimes beneath closed canopies and tree-fall gaps are compared for five temperate and tropical forests using fish-eye photography of intact forest canopies and a model for calculating light penetration through idealized gaps. Beneath intact canopies, analyses of canopy photographs indicate that sunflecks potentially contribute 37–68% of seasonal total photosynthetically active radiation. In all of the forests, potential sunfleck duration is brief (4–6 min), but the frequency distributions of potential sunfleck duration vary because of differences in canopy geometry and recent disturbance history. Analysis of the photographs reveals that incidence angles for photosynthetically active radiation beneath closed canopies are not generally vertical for any of the forests, but there was considerable variation both among and within sites in the contribution of overhead versus low-angle lighting. Calculations of light penetration through idealized single-tree gaps in old growth Douglas-fir – hemlock forests indicate that such gaps have little effect on understory light regimes because of the high ratio of canopy height to gap diameter. However, single-tree gaps in the other four forest types produce significant overall increases in understory light levels. There is also significant spatial variation in seasonal total radiation in and around single-tree gaps. Our results demonstrate that there can be significant penetration of light into the understory adjacent to a gap, particularly at high latitudes. As gap size increases, both the mean and the range of light levels within the gap increases, but even in large gaps (ca. 1000 m2) the potential duration of direct sunlight is generally brief (<4 h). The major differences in gap light regimes of the five forests are largely a function of canopy height and latitude. The effects of latitude should also result in differences in gap light regimes across the geographic range of individual forest types.
Gap dynamics in an Ohio Acer–Fagus forest and speculations on the geography of disturbance
Authors: Runkle James R.
Published: July 2008

Thirty-six forest gaps were monitored for 12 years in an old-growth forest dominated by Acersaccharum Marsh. and Fagusgrandifolia Ehrh. Most gaps were formed by single tree falls, although some larger ones were created by the deaths of two to four canopy trees. Gap closure rates suggest that most saplings need the occurrence of more than one gap to reach the canopy. Newer, small-scale disturbances, because of their geometry, occur near older disturbances at high rates. After gaps form, woody vegetation increases in density for 5–10 years and then decreases in density. The four main species of this study show different patterns of response, with optima as follows: small gaps of all ages for Acer, old gaps of all sizes for Fagus, large young gaps for Fraxinusamericana L., and large gaps of all ages for Liriodendrontulipifera L. The presence, size distribution, and species composition of saplings immediately preceding gap formation help determine which species will dominate the gap. In general, the processes occurring in gaps are sufficient to maintain the stand at its current canopy composition. A map of disturbances found in different parts of the eastern deciduous forest suggests that many forests, particularly those located near the center of the biome, renew themselves primarily by way of gaps.
Seed rain to tree-fall gaps in a Neotropical rain forest
Authors: Denslow Julie Sloan , Gomez Diaz Ana E.
Published: July 2008

We monitored both the seed rain and fruit production in the vicinity of four recent tree-fall gaps in the old-growth forest at the La Selva Biological Station, Costa Rica. Seeds were collected in trays of seed-sterilized soil distributed throughout the center of the gaps and left in place for 2 months; seeds were identified from seedlings that subsequently germinated from the soil samples in the shade house. Composition and density of seeds germinating from the trays were spatially and temporally variable, obscuring any phenological pattern in either species diversity or abundances of seedfall. However, rates of seed input (49 seeds/(m2•month)) were higher than previous estimates (0.5–5 seeds/(m•month)), which suggests a high turnover rate of soil seed stocks in forest species with short dormancy capacities. A small proportion of the seeds were from pioneer species (2–33%), which were nevertheless likely dispersed from second-growth vegetation at least 750 m from the gaps. Most of the species were animal dispersed and only 35% of the species and 19–55% of the seeds recovered from the seed trays likely originated from plants fruiting within 50 m of the gap. These data demonstrate the input of a copious and diverse seedfall from widely scattered sources within lowland tropical rain forests.
Canopy gaps in Douglas-fir forests of the Cascade Mountains
Authors: Spies Thomas A. , Franklin Jerry F. , Klopsch Mark
Published: July 2008

Types and rates of mortality were measured and canopy gap formation rates were estimated from 5- to 15-year records of mortality in 34 permanent plots in mature (100- to 150-year-old) and old-growth (>200-year-old) Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco)/western hemlock (Tsugacanadensis (Raf.) Sarg.) forests in western Oregon and Washington. Gap surveys were conducted in a mature and an old-growth stand, and characteristics of 40 gaps and regeneration were measured. Most canopy trees died without disrupting the forest in both mature (87.6%) and old-growth stands (73.3%). The amount of forest area per year representing new gaps was 0.7% in mature stands and 0.2% in old-growth stands. The gap survey found a higher proportion of gaps in the mature stand than in the old-growth stand. Most regeneration (> 1 m tall) in gaps was western hemlock; Douglas-fir regeneration did not occur. The ratio of seedling density in gaps to density under canopies was about 3 for the mature stand and about 9 for the old-growth stand. Seedling density was correlated with measures of gap age but not gap size. The study suggests that gap disturbances and vegetative responses are important processes in the dynamics of these forests. However, gap formation rates and vegetative responses appear to be slow relative to other forest types. In addition to gap size, canopy structure and disturbance severity are important determinants of gap response.
Phenylalanine and tyrosine kinetics in compensated liver cirrhosis: effects of meal ingestion
Authors: Tessari Paolo , Kiwanuka Edward , Vettore Monica , Barazzoni Rocco , Zanetti Michela , Cecchet Diego , Orlando Rocco
Published: July 2008

We explored the mechanism(s) of increased aromatic amino acids concentrations in liver cirrhosis using phenylalanine (Phe) and tyrosine (Tyr) isotope infusions in male patients with compensated cirrhosis (five in Child Class A, three in B) and in eight matched healthy controls, in both postabsorptive and fed states. After a baseline period, a standard liquid mixed meal was fed continuously over 4 h. Both a “plasma” and an intracellular model were employed. In the patients, steady-state Phe and Tyr concentrations were ∼30–50% greater, and rates of Phe appearance (Ra) (plasma model), Tyr Ra, and Phe hydroxylation (Hy; both models) were ∼25 to >100% greater than in controls in both states. Meal ingestion increased ( P < 0.05 or less vs. basal) Phe and Tyr concentrations, Phe and Tyr Ra, Phe Hy, and % Tyr Ra not deriving from Hy in both groups. Hy and Tyr Ra remained >50% greater ( P < 0.04 to P < 0.01) in patients, whereas Phe Ra was more modestly increased. Phe utilization for protein synthesis increased similarly in both groups. Tyr clearance was normal, whereas Phe clearance tended to be lower ( P = 0.09, intracellular model) in the patients. In summary, in compensated liver cirrhosis studied under fasted and fed states, 1) Tyr Ra is increased; 2) Phe Hy and Phe Ra (plasma model) are increased; 3) Tyr clearance is normal; and 4) Phe clearance is slightly decreased. In conclusion, in cirrhosis increased total tyrosine Ra and hydroxylation contribute to fasting and postmeal hypertyrosinemia, whereas the mechanism(s) responsible for the hyperphenylalaninemia may include both increased production and decreased disposal.
Essential fatty acid deficiency in mice impairs lactose digestion
Authors: Lukovac S. , Los E. L. , Stellaard F. , Rings E. H. H. M. , Verkade H. J.
Published: July 2008

Essential fatty acid (EFA) deficiency in mice induces fat malabsorption. We previously reported indications that the underlying mechanism is located at the level of the intestinal mucosa. We have investigated the effects of EFA deficiency on small intestinal morphology and function. Mice were fed an EFA-deficient or control diet for 8 wk. A 72-h fat balance, the EFA status, and small intestinal histology were determined. Carbohydrate absorptive and digestive capacities were assessed by stable isotope methodology after administration of [U-13C]glucose and [1-13C]lactose. The mRNA expression and enzyme activity of lactase, and concentrations of the EFA linoleic acid (LA) were measured in small intestinal mucosa. Mice fed the EFA-deficient diet were markedly EFA-deficient with a profound fat malabsorption. EFA deficiency did not affect the histology or proliferative capacity of the small intestine. Blood [13C6]glucose appearance and disappearance were similar in both groups, indicating unaffected monosaccharide absorption. In contrast, blood appearance of [13C]glucose, originating from [1-13C]lactose, was delayed in EFA-deficient mice. EFA deficiency profoundly reduced lactase activity (−58%, P < 0.01) and mRNA expression (−55%, P < 0.01) in mid-small intestine. Both lactase activity and its mRNA expression strongly correlated with mucosal LA concentrations ( r = 0.77 and 0.79, respectively, P < 0.01). EFA deficiency in mice inhibits the capacity to digest lactose but does not affect small intestinal histology. These data underscore the observation that EFA deficiency functionally impairs the small intestine, which in part may be mediated by low LA levels in the enterocytes.
The role of luminal factors in the recovery of gastric function and behavioral changes after chronicHelicobacter pyloriinfection
Authors: Verdu Elena F. , Bercik Premysl , Huang Xian Xi , Lu Jun , Al-Mutawaly Nafia , Sakai Hiromi , Tompkins Thomas A. , Croitoru Kenneth , Tsuchida Eihun , Perdue Mary , Collins Stephen M.
Published: July 2008

The role of chronic infections, such as Helicobacter pylori ( Hp), to produce sustained changes in host physiology remains controversial. In this study, we investigate whether the antigenic or bacterial content of the gut, after Hp eradication, influences the changes in gut function induced by chronic Hp infection. Mice were infected with Hp for 4 mo and then treated with antibiotics or placebo for 2 wk. Gastric emptying was measured using videofluoroscopy, feeding behavior using a 24-h feeding system, and intestinal permeability using an isolated jejunal segment arterially perfused with an artificial oxygen carrier, hemoglobin vesicles. Immune responses were assessed by CD3+cell counts and anti- Hp antibodies using ELISA. To determine the role of luminal factors in host physiology posteradication, groups of mice received the probiotics containing Lactobacillus rhamnosus R0011 and L. helveticus R0052 or placebo for 2 wk or crude Hp antigen weekly for 2 mo. Chronic Hp infection was associated with delayed gastric emptying, increased intestinal permeability, and increased gastric CD3+cell counts. Hp-induced altered feeding patterns did not reverse after eradication. Probiotics accelerated the recovery of paracellular permeability and delayed gastric emptying, improved the CD3+cell counts, and normalized altered feeding patterns posteradication. Hp antigen resulted in increased anti- Hp antibodies and increased CD3+cell counts in the stomach and delayed recovery of gastric function. Our results suggest that the bacterial content of the gut, as well as the presence of relevant antigens, influences the rate of recovery of host pathophysiology induced by chronic Hp infection. These changes do not seem to occur in association with modulation of intestinal permeability.
Electroacupuncture improves impaired gastric motility and slow waves induced by rectal distension in dogs
Authors: Chen Jie , Song Geng-Qing , Yin Jieyun , Koothan Thillai , Chen J. D. Z.
Published: July 2008

Rectal distension (RD) is known to induce upper gastrointestinal (GI) symptoms. The aim of this study was to investigate the effects and underlying mechanisms of RD on gastric slow waves (GSW) and motor activity and furthermore to investigate the effects and mechanisms of electroacupuncture (EA) on GSW and motor activity. Eight female hound dogs chronically implanted with gastric serosal electrodes and a gastric fistula were studied in six separate sessions. Antral motility, GSW, heart rate variability, and rectal pressure were evaluated for the above purposes. 1) RD at a volume of 120 ml suppressed antral motility significantly. Guanethidine blocked the inhibitory effect of RD. EA at ST36 was able to restore the suppressed antral contractions induced by RD (16.6 ± 1.7 vs. 8.0 ± 1.4, P < 0.001). Naloxone partially blocked the effect of EA on antral contractions. 2) RD reduced the percentage of normal GSW from 98.8 ± 0.8% at baseline to 76.1 ± 8.6% ( P < 0.05) that was increased to 91.8 ± 3.0% with EA. The effects of EA on the GSW were nullified by the presence of naloxone. 3) EA did not show any significant effect on rectal pressure, suggesting that the ameliorating effects of EA on RD-induced impaired gastric motility were not due to a decrease in rectal pressure. 4) EA increased the vagal activity suppressed by RD. In conclusion, RD inhibits postprandial gastric motility and impairs GSW in dogs, and the inhibitory effects are mediated via the adrenergic pathways. EA at ST36 is able to restore the RD-induced impaired GSW and motor activities, possibly by enhancing vagal activity, and is partially mediated via the opioid pathway. EA may have therapeutic potential for functional gastrointestinal disorders.
Innate immune adaptor MyD88 mediates neutrophil recruitment and myocardial injury after ischemia-reperfusion in mice
Authors: Feng Yan , Zhao Huailong , Xu Xinhua , Buys Emmanuel S. , Raher Michael J. , Bopassa Jean C. , Thibault Helene , Scherrer-Crosbie Marielle , Schmidt Ulrich , Chao Wei
Published: July 2008

MyD88 is an adaptor protein critical for innate immune response against microbial infection and in certain noninfectious tissue injury. The present study examined the role of MyD88 in myocardial inflammation and injury after ischemia-reperfusion (I/R). I/R was produced by coronary artery ligation for 30 min followed by reperfusion. The ratios of area at risk to left ventricle (LV) were similar between wild-type (WT) and MyD88-deficient (MyD88−/−) mice. However, 24 h after I/R, the ratios of myocardial infarction to area at risk were 58% less in MyD88−/− than in WT mice (14 ± 2% vs. 33 ± 6%, P = 0.01). Serial echocardiographic studies demonstrated that there was no difference in baseline LV contractile function between the two groups. Twenty-four hours after I/R, LV ejection fraction (EF) and fractional shortening (FS) in WT mice were reduced by 44% and 62% (EF, 51 ± 2%, and FS, 22 ± 1%, P < 0.001), respectively, and remained depressed on the seventh day after I/R. In comparison, EF and FS in MyD88−/− mice were 67 ± 3% and 33 ± 2%, respectively, after I/R ( P < 0.001 vs. WT). Similarly, LV function, as demonstrated by invasive hemodynamic measurements, was better preserved in MyD88−/− compared with WT mice after I/R. Furthermore, when compared with WT mice, MyD88−/− mice subjected to I/R had a marked decrease in myocardial inflammation as demonstrated by attenuated neutrophil recruitment and decreased expression of the proinflammatory mediators keratinocyte chemoattractant, monocyte chemoattractant protein-1, and ICAM-1. Taken together, these data suggest that MyD88 modulates myocardial inflammatory injury and contributes to myocardial infarction and LV dysfunction during I/R.
Aldosterone induces interleukin-18 through endothelin-1, angiotensin II, Rho/Rho-kinase, and PPARs in cardiomyocytes
Authors: Doi Takashi , Sakoda Tsuyoshi , Akagami Takafumi , Naka Toshio , Mori Yoshitomo , Tsujino Takeshi , Masuyama Tohru , Ohyanagi Mitsumasa
Published: July 2008

Aldosterone (Aldo) is recognized as an important risk factor for cardiovascular diseases. IL-18 induces myocardial hypertrophy, loss of contractility of cardiomyocytes, and apoptosis leading myocardial dysfunction. However, so far, there have been few reports concerning the interaction between Aldo and IL-18. The present study examined the effects and mechanisms of Aldo on IL-18 expression and the roles of peroxisome proliferator-activated receptor (PPAR) agonists in rat cardiomyocytes. We used cultured rat neonatal cardiomyocytes stimulated with Aldo to measure IL-18 mRNA and protein expression, Rho-kinase, and NF-κB activity. We also investigated the effects of PPAR agonists on these actions. Aldo, endothelin-1 (ET-1), and angiotensin II (ANG II) increased IL-18 mRNA and protein expression. Mineralocorticoid receptor antagonists, endothelin A receptor antagonist, and ANG II receptor antagonist inhibited Aldo-induced IL-18 expression. Aldo induced ET-1 and ANG II production in cultured media. Moreover, Rho/Rho-kinase inhibitor and statin inhibited Aldo-induced IL-18 expression. On the other hand, Aldo upregulated the activities of Rho-kinase and NF-κB. PPAR agonists attenuated the Aldo-induced IL-18 expression and NF-κB activity but not the Rho-kinase activity. Our findings indicate that Aldo induces IL-18 expression through a mechanism that involves, at a minimum, ET-1 and ANG II acting via the Rho/Rho-kinase and PPAR/NF-κB pathway. The induction of IL-18 in cardiomyocytes by Aldo, ET-1, and ANG II might, therefore, cause a deterioration of the cardiac function in an autocrine and paracrine fashion. The inhibition of the IL-18 expression by PPAR agonists might be one of the mechanisms whereby the beneficial cardiovascular effects are exerted.
Cardiac magnetic resonance imaging of myocardial contrast uptake and blood flow in patients affected with idiopathic or familial dilated cardiomyopathy
Authors: Jerosch-Herold Michael , Sheridan David C. , Kushner Jessica D. , Nauman Deirdre , Burgess Donna , Dutton Diana , Alharethi Rami , Li Duanxiang , Hershberger Ray E.
Published: July 2008

Idiopathic dilated cardiomyopathy (IDC) is characterized by left ventricular (LV) enlargement with systolic dysfunction, other causes excluded. When inherited, it represents familial dilated cardiomyopathy (FDC). We hypothesized that IDC or FDC would show with cardiac magnetic resonance (CMR) increased myocardial accumulation of gadolinium contrast at steady state and decreased baseline myocardial blood flow (MBF) due to structural alterations of the extracellular matrix compared with normal myocardium. CMR was performed in nine persons affected with IDC/FDC. Healthy controls came from the general population ( n = 6) or were unaffected family members of FDC patients ( n = 3) without signs or symptoms of IDC/FDC or any structural cardiac abnormalities. The myocardial partition coefficient for gadolinium contrast (λGd) was determined by T1 measurements. LV shape and function and MBF were assessed by standard CMR methods. λGd was elevated in IDC/FDC patients vs. healthy controls (λGd = 0.56 ± 0.15 vs. 0.41 ± 0.06; P = 0.002), and correlated with LV enlargement ( r = 0.61 for λGd vs. end-diastolic volume indexed by height; P < 0.01) and with ejection fraction ( r = −0.80; P < 0.001). The extracellular volume fraction was higher in IDC patients than in healthy controls (0.31 ± 0.05 vs. 0.24 ± 0.03; P = 0.002). Resting MBF was lower in IDC patients (0.64 ± 0.13 vs. 0.91 ± 0.22; P = 0.01) than unaffected controls and correlated with both the partition coefficient ( r = −0.57; P = 0.012) and the extracellular volume fraction ( r = −0.56; P = 0.019). The expansion of the extracellular space correlated with reduced MBF and ventricular dilation. Expansion of the extracellular matrix may be a key contributor to contractile dysfunction in IDC patients.
Impact of anaerobic glycolysis and oxidative substrate selection on contractile function and mechanical efficiency during moderate severity ischemia
Authors: Zhou Lufang , Huang Hazel , McElfresh Tracy A. , Prosdocimo Domenick A. , Stanley William C.
Published: July 2008

The role of anaerobic glycolysis and oxidative substrate selection on contractile function and mechanical efficiency during moderate severity myocardial ischemia is unclear. We hypothesize that 1) preventing anaerobic glycolysis worsens contractile function and mechanical efficiency and 2) increasing glycolysis and glucose oxidation while inhibiting free fatty acid oxidation improves contractile function during ischemia. Experiments were performed in anesthetized pigs, with regional ischemia induced by a 60% decrease in left anterior descending coronary artery blood flow for 40 min. Three groups were studied: 1) no treatment, 2) inhibition of glycolysis with iodoacetate (IAA), or 3) hyperinsulinemia and hyperglycemia (HI + HG). Glucose and free fatty acid oxidation were measured using radioisotopes and anaerobic glycolysis from net lactate efflux and myocardial lactate content. Regional contractile power was assessed from left ventricular pressure and segment length in the anterior wall. We found that preventing anaerobic glycolysis with IAA during ischemia in the absence of alterations in free fatty acid and glucose oxidation did not adversely affect contractile function or mechanical efficiency during myocardial ischemia, suggesting that anaerobic glycolysis is not essential for maintaining residual contractile function. Increasing glycolysis and glucose oxidation with HI + HG inhibited free fatty acid oxidation and improved contractile function and mechanical efficiency. In conclusion, these results show a dissociation between myocardial function and anaerobic glycolysis during moderate severity ischemia in vivo, suggesting that metabolic therapies should not be aimed at inhibiting anaerobic glycolysis per se, but rather activating insulin signaling and/or enhancing carbohydrate oxidation and/or decreasing fatty acid oxidation.
Pressure-distension relationship in arteries and arterioles in response to 5 wk of horizontal bedrest
Authors: Eiken Ola , Kölegård Roger , Mekjavic Igor B.
Published: July 2008

We hypothesized that exposure to prolonged recumbency (bedrest), and thus reductions of intravascular pressure gradients, increases pressure distension in arteries/arterioles in the legs. Ten subjects underwent 5 wk of horizontal bedrest. Pressure distension was investigated in arteries and arterioles before and after the bedrest, with the subject seated or supine in a hyperbaric chamber with either one arm or a lower leg protruding through a hole in the chamber door. Increased pressure in the vessels of the arm/leg was accomplished by increasing chamber pressure. Vessel diameter and flow were measured in the brachial and posterior tibial arteries using Doppler ultrasonography. Electrical tissue impedance was measured in the test limb. Bedrest increased ( P < 0.01) pressure distension threefold in the tibial artery (from 8 ± 7% to 24 ± 11%) and by a third ( P < 0.05) in the brachial artery (from 15 ± 9% to 20 ± 10%). The pressure-induced increase in tibial artery flow was more pronounced ( P < 0.01) after (50 ± 39 ml/min) than before (13 ± 23 ml/min) bedrest, whereas the brachial artery flow response was unaffected by bedrest. The pressure-induced decrease in tissue impedance in the leg was more pronounced ( P < 0.01) after (16 ± 7%) than before (10 ± 6%) bedrest, whereas bedrest did not affect the impedance response in the arm. Thus, withdrawal of the hydrostatic pressure gradients that act along the blood vessels in erect posture markedly increases pressure distension in dependent arteries and arterioles.
A noninvasive analysis of urinary musculoskeletal collagen metabolism markers from rhesus monkeys subject to chronic hypergravity
Authors: Martinez D. A. , Patterson-Buckendahl P. E. , Lust A. , Shea-Rangel K. M. , Hoban-Higgins T. M. , Fuller C. A. , Vailas A. C.
Published: July 2008

A decrease in load-bearing activity, as experienced during spaceflight or immobilization, affects the musculoskeletal system in animals and humans, resulting in the loss of bone and connective tissue. It has been suggested that hypergravity (HG) can counteract the deleterious effects of microgravity-induced musculoskeletal resorption. However, little consensus information has been collected on the noninvasive measurement of collagen degradation products associated with enhanced load-bearing stress on the skeleton. The purpose of this study is to assess the urinary collagen metabolic profiles of rhesus monkeys ( Macaca mulatta) during 1) 2 wk of basal 1 G (pre-HG), 2) 2 wk of HG (2 G), and 3) two periods of post-HG recovery (1 G). Urine was collected over a 24-h period from six individual rhesus monkeys. Hydroxyproline (Hyp) and collagen cross-links (hydroxylysylpyridinoline and lysylpyridinoline) were measured by reverse-phase HPLC. Urinary calcium, measured by atomic absorption, and creatinine were also assayed. The results indicate no changes in nonreducible cross-links and Hyp during HG. Collagen cross-link biomarker levels were significantly elevated during the 2nd wk of HG. Urinary calcium content was significantly lower during HG than during the 1-G control period, suggesting calcium retention by the body. We conclude that there is an adaptation of the nonhuman primate musculoskeletal system during hyperloading and that noninvasive measurements of musculoskeletal biomarkers can be used as indicators of collagen and mineral metabolism during HG and recovery in nonhuman primates.
Differential muscle function between muscle synergists: long and lateral heads of the triceps in jumping and landing goats (Capra hircus)
Authors: Carroll Andrew M. , Lee David V. , Biewener Andrew A.
Published: July 2008

We investigate how the biarticular long head and monoarticular lateral head of the triceps brachii function in goats ( Capra hircus) during jumping and landing. Elbow moment and work were measured from high-speed video and ground reaction force (GRF) recordings. Muscle activation and strain were measured via electromyography and sonomicrometry, and muscle stress was estimated from elbow moment and by partitioning stress based on its relative strain rate. Elbow joint and muscle function were compared among three types of limb usage: jump take-off (lead limb), the step prior to jump take-off (lag limb), and landing. We predicted that the strain and work patterns in the monoarticular lateral head would follow the kinematics and work of the elbow more closely than would those of the biarticular long head. In general this prediction was supported. For instance, the lateral head stretched (5 ± 2%; mean ± SE) in the lead and lag limbs to absorb work during elbow flexion and joint work absorption, while the long head shortened (−7 ± 1%) to produce work. During elbow extension, both muscles shortened by similar amounts (−10 ± 2% long; −13 ± 4% lateral) in the lead limb to produce work. Both triceps heads functioned similarly in landing, stretching (13 ± 3% in the long head and 19 ± 5% in the lateral) to absorb energy. In general, the long head functioned to produce power at the shoulder and elbow, while the lateral head functioned to resist elbow flexion and absorb work, demonstrating that functional diversification can arise between mono- and biarticular muscle agonists operating at the same joint.
Na+ secretion rate increases proportionally more than the Na+ reabsorption rate with increases in sweat rate
Authors: Buono Michael J. , Claros Ryan , DeBoer Teshina , Wong Janine
Published: July 2008

The purpose of this study was to measure the in vivo Na+ secretion and Na+ reabsorption rates of the human eccrine sweat gland with increases in sweat rate. Such data should help to elucidate the physiological mechanism responsible for the previously reported linear relationship between increases in sweat rate and Na+ concentration in sweat. On 5 days, each subject ( n = 10) completed a 30-min exercise bout in an environmental chamber set at 35°C and 40% relative humidity. The intensity for the five exercise bouts in the heat was set to approximate 50, 60, 70, 80, and 90% of age-predicted maximum heart rate. Forearm sweat samples and capillary blood samples were collected during each of the five 30-min exercise bouts. The sweat and blood samples were analyzed for Na+ concentration in sweat and serum, which were used to calculate the rate of Na+ secretion and Na+ reabsorption. The mean correlation between sweat rate and Na+ concentration in sweat was found to be r = 0.73. Within the sweat rate range of the present study, both Na+ secretion rate and Na+ reabsorption rate increased linearly; however, the Na+ secretion rate increased almost twice as fast (slope = 141 vs. 80). Thus the rate at which Na+ escaped reabsorption increased with increases in sweat rate and was significantly ( P < 0.05) correlated to the Na+ concentration in sweat (mean r = 0.90). Such results strongly suggest that the physiological mechanism responsible for the previously reported linear increase in Na+ concentration in sweat seen with increases in sweat rate is that the Na+ secretion rate increases proportionally more than the Na+ reabsorption rate.
Gene expression during inactivity-induced muscle atrophy: effects of brief bouts of a forceful contraction countermeasure
Authors: Kim Soo J. , Roy Roland R. , Kim Jung A. , Zhong Hui , Haddad Fadia , Baldwin Kenneth M. , Edgerton V. Reggie
Published: July 2008

Anabolic and catabolic markers of muscle protein metabolism were examined in inactivity-induced atrophying muscles with and without daily short-duration, high-resistance isometric contractions. Inactivity was achieved via spinal cord isolation (SI), which results in near inactivity of the hindlimb musculature without compromising the motoneuron-muscle connectivity. Adult rats were assigned to a control (Con) or SI group in which one limb was stimulated (SI-Stim, 5 consecutive days of brief bouts of high-load isometric contractions) while the other served as a SI control (SI). Both the medial gastrocnemius (MG) and soleus weights (relative to body weight) were ∼71% of Con in the SI, but maintained at Con in the SI-Stim group. Activity of the IGF-1/phosphatidylinositol 3-kinase (PI3K)/Akt pathway of protein synthesis was similar among all groups in the MG. Expression of atrogin-1 and muscle RING finger-1 (MuRF-1), markers of protein degradation, were higher in the MG and soleus of the SI than Con and maintained at Con in the SI-Stim. Compared with Con, the anti-growth factor myostatin was unaffected in the MG and soleus in the SI but was lower in the MG of the SI-Stim. These results demonstrate that upregulation of specific protein catabolic pathways plays a critical role in SI-induced atrophy, while this response was blunted by 4 min of daily high-resistance electromechanical stimulation and was able to preserve most of the muscle mass. Although the protein anabolic pathway (IGF-1/PI3K/Akt) appears to play a minor role in regulating mass in the SI model, increased translational capacity may have contributed to mass preservation in response to isometric contractions.