Displaying publications 21 - 40 of 405 in total

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  1. Fulltext Body fat measurement among Singaporean Chinese, Malays and Indians: a comparative study using a four-compartment model and different two-compartment models
    Deurenberg-Yap M, Schmidt G, van Staveren WA, Hautvast JG, Deurenberg P
    Br J Nutr, 2001 Apr;85(4):491-8.
    PMID: 11348564 DOI: 10.1079/bjn2000276
    This cross-sectional study compared body fat percentage (BF%) obtained from a four-compartment (4C) model with BF% from hydrometry (using 2H2O), dual-energy X-ray absorptiometry (DXA) and densitometry among the three main ethnic groups (Chinese, Malays and Indians) in Singapore, and determined the suitability of two-compartment (2C) models as surrogate methods for assessing BF% among different ethnic groups. A total of 291 subjects (108 Chinese, seventy-six Malays, 107 Indians) were selected to ensure an adequate representation of age range (18-75 years) and BMI range (16-40 kg/m2) of the general adult population, with almost equal numbers from each gender group. Body weight was measured, together with body height, total body water by 2H2O dilution, densitometry with Bodpod and bone mineral content with Hologic QDR-4500. BF% measurements with a 4C model for the subgroups were: Chinese females 33.5 (sd 7.5), Chinese males 24.4 (sd 6.1), Malay females 37.8 (sd 6.3), Malay males 26.0 (sd 7.6), Indian females 38.2 (sd 7.0), Indian males 28.1 (sd 5.5). Differences between BF% measured by the 4C and 2C models (hydrometry, DXA and densitometry) were found, with underestimation of BF% in all the ethnic-gender groups by DXA of 2.1-4.2 BF% and by densitometry of 0.5-3.2 BF%). On a group level, the differences in BF% between the 4C model and 2H2O were the lowest (0.0-1.4 BF% in the different groups), while differences between the 4C model and DXA were the highest. Differences between the 4C model and 2H2O and between the 4C model and DXA were positively correlated with the 4C model, water fraction (f(water)) of fat-free mass (FFM) and the mineral fraction (f(mineral)) of FFM, and negatively correlated with density of the FFM (D(FFM)), while the difference between 4C model and densitometry correlated with these variables negatively and positively respectively (i.e. the correlations were opposite). The largest contributors to the observed differences were f(water) and D(FFM). When validated against the reference 4C model, 2C models were found to be unsuitable for accurate measurements of BF% at the individual level, owing to the high errors and violation of assumptions of constant hydration of FFM and D(FFM) among the ethnic groups. On a group level, the best 2C model for measuring BF% among Singaporeans was found to be 2H2O.
    Matched MeSH terms: Models, Biological*
  2. Theoretically-derived molecular descriptors important in human intestinal absorption
    Agatonovic-Kustrin S, Beresford R, Yusof AP
    J Pharm Biomed Anal, 2001 May;25(2):227-37.
    PMID: 11275432
    A quantitative structure-human intestinal absorption relationship was developed using artificial neural network (ANN) modeling. A set of 86 drug compounds and their experimentally-derived intestinal absorption values used in this study was gathered from the literature and a total of 57 global molecular descriptors, including constitutional, topological, chemical, geometrical and quantum chemical descriptors, calculated for each compound. A supervised network with radial basis transfer function was used to correlate calculated molecular descriptors with experimentally-derived measures of human intestinal absorption. A genetic algorithm was then used to select important molecular descriptors. Intestinal absorption values (IA%) were used as the ANN's output and calculated molecular descriptors as the inputs. The best genetic neural network (GNN) model with 15 input descriptors was chosen, and the significance of the selected descriptors for intestinal absorption examined. Results obtained with the model that was developed indicate that lipophilicity, conformational stability and inter-molecular interactions (polarity, and hydrogen bonding) have the largest impact on intestinal absorption.
    Matched MeSH terms: Models, Biological
  3. Keloids - the sebum hypothesis revisited
    Fong EP, Bay BH
    Med Hypotheses, 2002 Apr;58(4):264-9.
    PMID: 12027517
    The aetiology of the keloid scar has not been completely elucidated. Numerous hypotheses have been proposed in the past to explain the unusual characteristics of the keloid scar. While we do know that there is excessive and ongoing collagen-deposition, the exact triggering stimulus is a subject of conjecture. We present some of our photographic records of keloids and electron microscopic findings of keloid edges and reiterate the sebum hypothesis. We also attempt to explain the features of keloids in the light of the present knowledge of immunology and cell biology.
    Matched MeSH terms: Models, Biological*
  4. Validity of deuterium oxide dilution for the measurement of body fat among Singaporeans
    Deurenberg-Yap M, Deurenberg P
    Food Nutr Bull, 2002 Sep;23(3 Suppl):34-7.
    PMID: 12362808
    Body fat percent (BF%) was measured in 108 adult Chinese, 76 Malays, and 107 Indians in Singapore by densitometry, deuterium oxide dilution (hydrometry), dual energy x-ray absorptiometry (DXA) and a chemical four-compartment model (BF%4c). The hydration of the fat-free mass (FFM) was calculated. Subjects ranged in age from 18 to 69 years and their body mass index ranged from 16 to 40 kg/m2. BF%4c for the various subgroups were: Chinese females (33.5 +/- 7.5%), Chinese males (24.4 +/- 6.1%), Malay females (37.8 +/- 6.3%), Malay males (26.0 +/- 7.6%), Indian females (38.2 +/- 7.0%) and Indian males (28.1 +/- 5.5%). Biases were found between BF%4c and BF% measured by 2-compartment models (hydrometry, densitometry, DXA), with systematic underestimation by DXA and densitometry. On a group level hydrometry had the lowest bias while DXA gave the highest bias. When validated against BF%4c, 2-compartment models were found to be unsuitable for accurate measures of body fat due to high biases at the individual level and the violation of assumptions of constant hydration of FFM and density FFM among the ethnic groups. On a group level the best 2-compartment model for measuring body fat was found to be hydrometry.
    Matched MeSH terms: Models, Biological*
  5. A simplified approach for exit dose in vivo measurements in radiotherapy and its clinical application
    Banjade DP, Shrestha SL, Shukri A, Tajuddin AA, Bhat M
    Australas Phys Eng Sci Med, 2002 Sep;25(3):110-8.
    PMID: 12416587
    This is a study using LiF:Mg;Ti thermoluminescent dosimeter (TLD) rods in phantoms to investigate the effect of lack of backscatter on exit dose. Comparing the measured dose with anticipated dose calculated using tissue maximum ratio (TMR) or percentage depth dose (PDD) gives rise to a correction factor. This correction factor may be applied to in-vivo dosimetry results to derive true dose to a point within the patient. Measurements in a specially designed humanoid breast phantom as well as patients undergoing radiotherapy treatment were also been done. TLDs with reproducibility of within +/- 3% (1 SD) are irradiated in a series of measurements for 6 and 10 MV photon beams from a medical linear accelerator. The measured exit doses for the different phantom thickness for 6 MV beams are found to be lowered by 10.9 to 14.0% compared to the dose derived from theoretical estimation (normalized dose at dmax). The same measurements for 10 MV beams are lowered by 9.0 to 13.5%. The variations of measured exit dose for different field sizes are found to be within 2.5%. The exit doses with added backscatter material from 2 mm up to 15 cm, shows gradual increase and the saturated values agreed within 1.5% with the expected results for both beams. The measured exit doses in humanoid breast phantom as well as in the clinical trial on patients undergoing radiotherapy also agreed with the predicted results based on phantom measurements. The authors' viewpoint is that this technique provides sufficient information to design exit surface bolus to restore build down effect in cases where part of the exit surface is being considered as a target volume. It indicates that the technique could be translated for in vivo dose measurements, which may be a conspicuous step of quality assurance in clinical practice.
    Matched MeSH terms: Models, Biological
  6. Defining and measuring trophic role similarity in food webs using regular equivalence
    Luczkovich JJ, Borgatti SP, Johnson JC, Everett MG
    J Theor Biol, 2003 Feb 07;220(3):303-21.
    PMID: 12468282
    We present a graph theoretic model of analysing food web structure called regular equivalence. Regular equivalence is a method for partitioning the species in a food web into "isotrophic classes" that play the same structural roles, even if they are not directly consuming the same prey or if they do not share the same predators. We contrast regular equivalence models, in which two species are members of the same trophic group if they have trophic links to the same set of other trophic groups, with structural equivalence models, in which species are equivalent if they are connected to the exact same other species. Here, the regular equivalence approach is applied to two published food webs: (1) a topological web (Malaysian pitcher plant insect food web) and (2) a carbon-flow web (St. Marks, Florida seagrass ecosystem food web). Regular equivalence produced a more satisfactory set of classes than did the structural approach, grouping basal taxa with other basal taxa and not with top predators. Regular equivalence models provide a way to mathematically formalize trophic position, trophic group and trophic niche. These models are part of a family of models that includes structural models used extensively by ecologists now. Regular equivalence models uncover similarities in trophic roles at a higher level of organization than do the structural models. The approach outlined is useful for measuring the trophic roles of species in food web models, measuring similarity in trophic relations of two or more species, comparing food webs over time and across geographic regions, and aggregating taxa into trophic groups that reduce the complexity of ecosystem feeding relations without obscuring network relationships. In addition, we hope the approach will prove useful in predicting the outcome of predator-prey interactions in experimental studies.
    Matched MeSH terms: Models, Biological*
  7. Sexual selection on land snail shell ornamentation: a hypothesis that may explain shell diversity
    Schilthuizen M
    BMC Evol. Biol., 2003 Jun 05;3:13.
    PMID: 12791170
    BACKGROUND: Many groups of land snails show great interspecific diversity in shell ornamentation, which may include spines on the shell and flanges on the aperture. Such structures have been explained as camouflage or defence, but the possibility that they might be under sexual selection has not previously been explored.

    PRESENTATION OF THE HYPOTHESIS: The hypothesis that is presented consists of two parts. First, that shell ornamentation is the result of sexual selection. Second, that such sexual selection has caused the divergence in shell shape in different species.

    TESTING THE HYPOTHESIS: The first part of the hypothesis may be tested by searching for sexual dimorphism in shell ornamentation in gonochoristic snails, by searching for increased variance in shell ornamentation relative to other shell traits, and by mate choice experiments using individuals with experimentally enhanced ornamentation. The second part of the hypothesis may be tested by comparing sister groups and correlating shell diversity with degree of polygamy.

    IMPLICATIONS OF THE HYPOTHESIS: If the hypothesis were true, it would provide an explanation for the many cases of allopatric evolutionary radiation in snails, where shell diversity cannot be related to any niche differentiation or environmental differences.

    Matched MeSH terms: Models, Biological
  8. Ethanol fermentation in an immobilized cell reactor using Saccharomyces cerevisiae
    Najafpour G, Younesi H, Syahidah Ku Ismail K
    Bioresour Technol, 2004 May;92(3):251-60.
    PMID: 14766158
    Fermentation of sugar by Saccharomyces cerevisiae, for production of ethanol in an immobilized cell reactor (ICR) was successfully carried out to improve the performance of the fermentation process. The fermentation set-up was comprised of a column packed with beads of immobilized cells. The immobilization of S. cerevisiae was simply performed by the enriched cells cultured media harvested at exponential growth phase. The fixed cell loaded ICR was carried out at initial stage of operation and the cell was entrapped by calcium alginate. The production of ethanol was steady after 24 h of operation. The concentration of ethanol was affected by the media flow rates and residence time distribution from 2 to 7 h. In addition, batch fermentation was carried out with 50 g/l glucose concentration. Subsequently, the ethanol productions and the reactor productivities of batch fermentation and immobilized cells were compared. In batch fermentation, sugar consumption and ethanol production obtained were 99.6% and 12.5% v/v after 27 h while in the ICR, 88.2% and 16.7% v/v were obtained with 6 h retention time. Nearly 5% ethanol production was achieved with high glucose concentration (150 g/l) at 6 h retention time. A yield of 38% was obtained with 150 g/l glucose. The yield was improved approximately 27% on ICR and a 24 h fermentation time was reduced to 7 h. The cell growth rate was based on the Monod rate equation. The kinetic constants (K(s) and mu(m)) of batch fermentation were 2.3 g/l and 0.35 g/lh, respectively. The maximum yield of biomass on substrate (Y(X-S)) and the maximum yield of product on substrate (Y(P-S)) in batch fermentations were 50.8% and 31.2% respectively. Productivity of the ICR were 1.3, 2.3, and 2.8 g/lh for 25, 35, 50 g/l of glucose concentration, respectively. The productivity of ethanol in batch fermentation with 50 g/l glucose was calculated as 0.29 g/lh. Maximum production of ethanol in ICR when compared to batch reactor has shown to increase approximately 10-fold. The performance of the two reactors was compared and a respective rate model was proposed. The present research has shown that high sugar concentration (150 g/l) in the ICR column was successfully converted to ethanol. The achieved results in ICR with high substrate concentration are promising for scale up operation. The proposed model can be used to design a lager scale ICR column for production of high ethanol concentration.
    Matched MeSH terms: Models, Biological
  9. Fulltext Modeling of hemoglobin in dengue fever and dengue hemorrhagic fever using bioelectrical impedance
    Ibrahim F, Ismail NA, Taib MN, Wan Abas WA
    Physiol Meas, 2004 Jun;25(3):607-15.
    PMID: 15253113 DOI: 10.1088/0967-3334/25/3/002
    This paper describes a model for predicting hemoglobin (Hb) by using bioelectrical impedance analysis (BIA) in dengue patients in the Hospital Universiti Kebangsaan Malaysia (HUKM). Bioelectrical impedance measurements were conducted on 83 (47 males and 36 females) serologically confirmed dengue fever (DF) and dengue hemorrhagic fever (DHF) patients during their hospitalization. The predictive equation for Hb was derived using multivariate analysis. We investigated all the parameters in BIA, patients' symptom and demographic data. In this developed model, four predictors (reactance (XC), sex, weight and vomiting) were found to be the best predictive factors for modeling Hb in dengue patients. However, the model can only explain approximately 42% of the variation in Hb status, thus single frequency bio-impedance stand-alone technique is insufficient to monitor Hb for the DF and DHF patients. Further investigation using multi-frequency BIA is recommended in modeling Hb to achieve the most parsimonious model.
    Matched MeSH terms: Models, Biological*
  10. Therapeutic angiogenesis for severe ischemic heart diseases by autologous bone marrow cells transplantation
    Hattori R, Matsubara H
    Mol Cell Biochem, 2004 Sep;264(1-2):151-5.
    PMID: 15544044
    Conventional therapies for severe ischemic heart disease are limited in applicability. While several angiogenesis researches have shown novel efficacy, safety and feasibility for clinical use, recently we have started the clinical trial of a sole cell therapy using autologous bone marrow mononuclear cells transplantation targeted into ischemic hibernating myocardium. Here, we review the background of bone marrow cell research and introduce therapeutic angiogenesis for severe ischemic heart disease by autologous bone marrow cells transplantation.
    Matched MeSH terms: Models, Biological
  11. Automatic generation of controllers for embodied legged organisms: a Pareto evolutionary multi-objective approach
    Teo J, Abbass HA
    Evol Comput, 2004;12(3):355-94.
    PMID: 15355605
    In this paper, we investigate the use of a self-adaptive Pareto evolutionary multi-objective optimization (EMO) approach for evolving the controllers of virtual embodied organisms. The objective of this paper is to demonstrate the trade-off between quality of solutions and computational cost. We show empirically that evolving controllers using the proposed algorithm incurs significantly less computational cost when compared to a self-adaptive weighted sum EMO algorithm, a self-adaptive single-objective evolutionary algorithm (EA) and a hand-tuned Pareto EMO algorithm. The main contribution of the self-adaptive Pareto EMO approach is its ability to produce sufficiently good controllers with different locomotion capabilities in a single run, thereby reducing the evolutionary computational cost and allowing the designer to explore the space of good solutions simultaneously. Our results also show that self-adaptation was found to be highly beneficial in reducing redundancy when compared against the other algorithms. Moreover, it was also shown that genetic diversity was being maintained naturally by virtue of the system's inherent multi-objectivity.
    Matched MeSH terms: Models, Biological*
  12. Optimization of medium composition for the production of a probiotic microorganism, Lactobacillus rhamnosus, using response surface methodology
    Liew SL, Ariff AB, Raha AR, Ho YW
    Int J Food Microbiol, 2005 Jul 15;102(2):137-42.
    PMID: 15992613
    This study was undertaken to optimize yeast extract, glucose, and vitamin concentrations; and also culture pH for maximizing the growth of a probiotic bacterium, Lactobacillus rhamnosus, and to assess the effects of these factors by using response surface methodology. A central composite design was used as an experimental design for the allocation of treatment combinations. A polynomial regression model with cubic and quartic terms was used for analysis of the experimental data. It was found that the effects involving yeast extract, glucose, vitamins and pH on the growth of L. rhamnosus were significant, and the strongest effect was given by the yeast extract concentration. Estimated optimum conditions of the factors for the growth of L. rhamnosus are as follows: pH=6.9; vitamin solution=1.28% (v/v); glucose=5.01% (w/v) and yeast extract=6.0% (w/v).
    Matched MeSH terms: Models, Biological
  13. Density dependence explains tree species abundance and diversity in tropical forests
    Volkov I, Banavar JR, He F, Hubbell SP, Maritan A
    Nature, 2005 Dec 1;438(7068):658-61.
    PMID: 16319890
    The recurrent patterns in the commonness and rarity of species in ecological communities--the relative species abundance--have puzzled ecologists for more than half a century. Here we show that the framework of the current neutral theory in ecology can easily be generalized to incorporate symmetric density dependence. We can calculate precisely the strength of the rare-species advantage that is needed to explain a given RSA distribution. Previously, we demonstrated that a mechanism of dispersal limitation also fits RSA data well. Here we compare fits of the dispersal and density-dependence mechanisms for empirical RSA data on tree species in six New and Old World tropical forests and show that both mechanisms offer sufficient and independent explanations. We suggest that RSA data cannot by themselves be used to discriminate among these explanations of RSA patterns--empirical studies will be required to determine whether RSA patterns are due to one or the other mechanism, or to some combination of both.
    Matched MeSH terms: Models, Biological*
  14. Relevance of diffusion through bacterial spore coats/membranes and the associated concentration boundary layers in the initial lag phase of inactivation: a case study for Bacillus subtilis with ozone and monochloramine
    Fernando WJ, Othman R
    Math Biosci, 2006 Feb;199(2):175-87.
    PMID: 16387333
    Disinfectants are generally used to inactivate microorganisms in solutions. The process of inactivation involves the disinfectant in the liquid diffusing towards the bacteria sites and thereafter reacting with bacteria at rates determined by the respective reaction rates. Such processes have demonstrated an initial lag phase followed by an active depletion phase of bacteria. This paper attempts to study the importance of the combined effects of diffusion of the disinfectant through the outer membrane of the bacteria and transport through the associated concentration boundary layers (CBLs) during the initial lag phase. Mathematical equations are developed correlating the initial concentration of the disinfectant with time required for reaching a critical concentration (C*) at the inner side of the membrane of the cell based on diffusion of disinfectant through the outer membranes of the bacteria and the formation of concentration boundary layers on both sides of the membranes. Experimental data of the lag phases of inactivation already available in the literature for inactivation of Bacillus subtilis spores with ozone and monochloramine are tested with the equations. The results seem to be in good agreement with the theoretical equations indicating the importance of diffusion process across the outer cell membranes and the resulting CBL's during the lag phase of disinfection.
    Matched MeSH terms: Models, Biological*
  15. Corneal elevation indices in normal and keratoconic eyes
    Fam HB, Lim KL
    J Cataract Refract Surg, 2006 Aug;32(8):1281-7.
    PMID: 16863962 DOI: 10.1016/j.jcrs.2006.02.060
    PURPOSE: To determine an index that distinguishes keratoconus and keratoconus-suspect eyes from normal eyes with Orbscan (Bausch & Lomb) corneal elevation maps.
    SETTING: Department of Ophthalmology, Tan Tock Seng Hospital, Singapore, and iLaser Centre, Island Hospital, Penang, Malaysia.
    METHODS: In this initial phase of this multicenter nonrandomized retrospective study, 1 eye of 166 normal subjects, 15 keratoconus patients, and 11 keratoconus suspects was examined at 1 clinic. The anterior best-fit sphere (BFS), posterior BFS, anterior elevation, posterior elevation, and maximum and minimum keratometries were analyzed. Two indices with the highest sensitivity and specificity classifying these conditions were identified using receiver operating characteristic curves. These 2 indices were evaluated in a subsequent validation study using 1 eye of 221 normal subjects, 43 keratoconus patients, and 23 keratoconus suspects from another clinic.
    RESULTS: The anterior elevation and anterior elevation ratio (anterior elevation ratio = anterior elevation/anterior BFS) best classified the different groups. An anterior elevation ratio of 0.5122 mm or less had 99% sensitivity and 95.2% specificity while a ratio 16.5 mum or less had 80.1% sensitivity and 80.8% specificity in discriminating normal eyes from keratoconus and keratoconus suspects. The results were similar in the validation study. In addition, these anterior elevation and anterior elevation ratio cutoff values had high sensitivity and specificity in identifying keratoconus suspects from normal eyes in the validation study.
    CONCLUSION: Anterior corneal elevation parameters are clinically relevant measures for detecting keratoconus and suspected keratoconus eyes.
    Matched MeSH terms: Models, Biological
  16. Improved production of live cells of Lactobacillus rhamnosus by continuous cultivation using glucose-yeast extract medium
    Ling LS, Mohamad R, Rahim RA, Wan HY, Ariff AB
    J Microbiol, 2006 Aug;44(4):439-46.
    PMID: 16953180
    In this study, the growth kinetics of Lactobacillus rhamnosus and lactic acid production in continuous culture were assessed at a range of dilution rates (0.05 h(-1) to 0.40 h(-1)) using a 2 L stirred tank fermenter with a working volume of 600 ml. Unstructured models, predicated on the Monod and Luedeking-Piret equations, were employed to simulate the growth of the bacterium, glucose consumption, and lactic acid production at different dilution rates in continuous cultures. The maximum specific growth rate of L. rhamnosus, mu-max, was estimated at 0.40 h(-1), and the Monod cell growth saturation constant, Ks, at approximately 0.25 g/L. Maximum cell viability (1.3 x 10(10) CFU/ml) was achieved in the dilution rate range of D = 0.28 h(-1) to 0.35 h(-1). Both maximum viable cell yield and productivity were achieved at D = 0.35 h(-1). The continuous cultivation of L. rhamnosus at D = 0.35 h(-1) resulted in substantial improvements in cell productivity, of 267% (viable cell count) that achieved via batch cultivation.
    Matched MeSH terms: Models, Biological
  17. Cyclic compression of chondrocytes modulates a purinergic calcium signalling pathway in a strain rate- and frequency-dependent manner
    Pingguan-Murphy B, El-Azzeh M, Bader DL, Knight MM
    J Cell Physiol, 2006 Nov;209(2):389-97.
    PMID: 16883605
    Mechanical loading modulates cartilage homeostasis through the control of matrix synthesis and catabolism. However, the mechanotransduction pathways through which chondrocytes detect different loading conditions remain unclear. The present study investigated the influence of cyclic compression on intracellular Ca2+ signalling using the well-characterised chondrocyte-agarose model. Cells labelled with Fluo4 were visualised using confocal microscopy following a period of 10 cycles of compression between 0% and 10% strain. In unstrained agarose constructs, not subjected to cyclic compression, a subpopulation of approximately 45% of chondrocytes exhibited spontaneous global Ca2+ transients with mean transient rise and fall times of 19.4 and 29.4 sec, respectively. Cyclic compression modulated global Ca2+ signalling by increasing the percentage of cells exhibiting Ca2+ transients (population modulation) and/or reducing the rise and fall times of these transients (transient shape modulation). The frequency and strain rate of compression differentially modulated these Ca2+ signalling characteristics providing a potential mechanism through which chondrocytes may distinguish between different loading conditions. Treatment with apyrase, gadolinium and the P2 receptor blockers, suramin and basilen blue, significantly reduced the percentage of cells exhibiting Ca2+ transients following cyclic compression, such that the mechanically induced upregulation of Ca2+ signalling was completely abolished. Thus cyclic compression appears to activate a purinergic pathway involving the release of ATP followed by the activation of P2 receptors causing a combination of extracellular Ca2+ influx and intracellular Ca2+ release. Knowledge of this fundamental cartilage mechanotransduction pathway may lead to improved therapeutic strategies for the treatment of cartilage damage and disease.
    Matched MeSH terms: Models, Biological
  18. Enhanced wound contraction and epithelization period in steroid treated rats: role of pyramid environment
    Kamath S, Rao SG, Murthy KD, Bairy KL, Bhat S
    Indian J Exp Biol, 2006 Nov;44(11):902-4.
    PMID: 17205711
    Contribution and role of a pyramid/square box on the wound healing suppressant effect of dexamethasone was studied in rats of either sex using excision wound model to record the wound contraction rate and epithelization period. The results showed enhanced wound contraction rate and decreased epithelization period in the pyramid-exposed rats as compared to controls. Thus, it appears that pyramid environment facilitates the process of wound healing. Also, the wound healing suppressant effects of dexamethasone were significantly reduced.
    Matched MeSH terms: Models, Biological
  19. Patchy stomatal behavior in broad-leaved trees grown in different habitats
    Takanashi S, Kosugi Y, Matsuo N, Tani M, Ohte N
    Tree Physiol, 2006 Dec;26(12):1565-78.
    PMID: 17169896
    Effects of heterogeneity in stomatal behavior on gas-exchange characteristics of leaves from four tree species growing in different climates, including temperate, tropical monsoon and tropical rain forest, were investigated by combining gas-exchange measurements and the pressure-infiltration method. Field observations indicated linear relationships between whole-leaf conductance and the ratio of infiltrated to non-infiltrated leaf area (open stomata area) in Dipterocarpus sublamellatus Foxw. and Neobalanocarpus heimii (King) Ashton in a tropical rain forest in Peninsular Malaysia, whereas the ratio of infiltrated to non-infiltrated area rapidly increased up to the whole-leaf conductance at which the entire leaf was infiltrated in Cinnamomum camphora Sieb. in a temperate evergreen forest in Japan and in Azadirachta indica Juss. in a tropical monsoon area in Thailand. These results strongly suggest small ranges in bell-shaped stomatal conductance distributions in C. camphora and A. indica and bimodal stomatal conductance distributions in D. sublamellatus and N. heimii. The values of normalized maximum carboxylation rate at 25 degrees C (V(cmax25)) derived from gas-exchange measurements were not constant, but decreased with decreasing whole-leaf conductance in D. sublamellatus and N. heimii. A gas-exchange model analysis revealed a linear relationship between whole-leaf conductance and the ratio of infiltrated to non-infiltrated leaf area for bimodal stomatal conductance distributions, whereas for bell-shaped distributions, the relationships were nonlinear. Midday depression of apparent V(cmax25) in these species was mainly caused by bimodal stomatal closure. The bimodal stomatal distribution model could also explain diurnal changes in photosynthetic assimilation and transpiration rates in these species.
    Matched MeSH terms: Models, Biological
  20. Influence of alignment of the pyramid on its beneficial effects
    Bhat S, Rao G, Murthy KD, Bhat PG
    Indian J Exp Biol, 2007 May;45(5):455-8.
    PMID: 17569288
    The present study was aimed to find out whether a change in the alignment of the pyramid from the north-south axis causes any variation in the effects produced by it on plasma cortisol levels and markers of oxidative stress in erythrocytes of adult-female Wistar rats. Plasma cortisol and erythrocyte TBARS levels were significantly lower whereas erythrocyte GSH was significantly higher in rats kept in pyramid that was aligned on the four cardinal points--north, east, south and west, as compared to normal control rats. Although there was a significant difference in the plasma cortisol level between normal control group and the group of rats kept in randomly aligned pyramid, there was no significant difference between these two groups for the other parameters. Erythrocyte TBARS levels in the group of rats kept in the randomly aligned pyramid was significantly higher than that in the group kept in the magnetically aligned pyramid. The results suggest that the north-south alignment of the pyramid is crucial for its expected effects.
    Matched MeSH terms: Models, Biological*
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