Strong association between polymorphisms in ANKH locus and skeletal size traits

Loss of bone strength is the main determinant of bone fragility. Bone strength is directly dependent on bone size (BS). A substantial portion of BS variation is attributable to genetic effects. However, the list of genes and allelic variants involved in the determination of BS variation is far from being complete. Polymorphisms in the ANKH gene have been shown to be associated with radiographic hand BS-related phenotypes. The present study examined the possible association of the ANKH gene with skeletal size and shape in order to test the universality of the ANKH effect on BS traits. Our sample consisted of a total of 212 ethnically homogeneous nuclear families (743 individuals) of European origin. Each individual was measured for body height, weight, and several other anthropometrical measurements, and genotyped for nine polymorphic markers (the average heterozygosity level was 0.4). We observed significant associations with practically all the anthropometrical phenotypes studied. More specifically, we found associations with body weight and height, limb length (P≤0.001; promoter region). After adjustment for body height, we demonstrated the substantial association increase for biacromial breadth (P=0.0012; some 140 kb downstream from ANKH) and vertebral column length (P=0.0008; exons 2–7 region). The majority of the observed associations persisted even after correction for multiple testing. For the first time the reliable evidence in support of universality of ANKH gene polymorphisms effect on bone size was provided.     

Effect of the melanocortin-3 receptor Thr6Lys and Val81Ile genetic variants on body composition and substrate oxidation in Chilean obese children

Mice genetically deficient in the melanocortin-3 receptor gene are characterized by normal body weight, increased body fat, mild hypophagia, reduced locomotor activity, and increased respiratory quotient compared with wild-type mice. In humans, the 6Lys–81Ile haplotype of melanocortin-3 receptor (MC3R) gene has been associated with childhood obesity, higher body fat percentage, and reduced fat oxidation compared to non-carriers. The aim of this study was to evaluate the association between MC3R 6Lys–81Ile haplotype with body composition and substrate oxidation in response to moderate exercise in obese children. Eight Chilean obese children (aged 8–12) carriers of MC3R 6Lys–81Ile haplotype were compared with eight age–gender-matched obese non-carriers. Children were identified through a previous cross-sectional study on genetic determinants of childhood obesity (n = 229). Genotypes for MC3R Thr6Lys and Val81Ile were determined by polymerase chain reaction–restriction fragment length polymorphism. Body composition was assessed by the four-compartment model (dual-energy X-ray absorptiometry, total body water by the deuterium dilution technique, and total fat mass by air-displacement plethysmography). Substrate oxidation was assessed by indirect calorimetry in response to moderate exercise (60% VO_{2 max}). Wilcoxon matched-pairs test was used to compare quantitative variables. No significant differences among carriers and non-carriers were found in anthropometrical and body composition measurements. The Carriers of the 6Lys–81Ile haplotype showed higher respiratory quotient (p = 0.06) and a significantly higher glucose oxidation (p = 0.01) compared with non-carriers after standardization for fat-free mass. Our results are consistent with a possible participation of MC3R 6Lys–81Ile variants in glucose oxidation in response to moderate exercise.     

Energetic cost of hovering flight in nectar-feeding bats (Phyllostomidae: Glossophaginae) and its scaling in moths, birds and bats

Three groups of specialist nectar-feeders covering a continuous size range from insects, birds and bats have evolved the ability for hovering flight. Among birds and bats these groups generally comprise small species, suggesting a relationship between hovering ability and size. In this study we established the scaling relationship of hovering power with body mass for nectar-feeding glossophagine bats (Phyllostomidae). Employing both standard and fast-response respirometry, we determined rates of gas exchange in Hylonycteris underwoodi (7 g) and Choeronycteris mexicana (13–18 g) during hover-feeding flights at an artificial flower that served as a respirometric mask to estimate metabolic power input. The O₂ uptake rate (V˙ _o2) in ml g⁻¹ h⁻¹ (and derived power input) was 27.3 (1.12 W or 160 W kg⁻¹) in 7-g Hylonycteris and 27.3 (2.63 W or 160 W kg⁻¹) in 16.5-g Choeronycteris and thus consistent with measurements in 11.9-g Glossophagasoricina (158 W kg⁻¹, Winter 1998). V˙ _o2 at the onset of hovering was also used to estimate power during forward flight, because after a transition from level forward to hovering flight gas exchange rates initially still reflect forward flight rates. V˙ _o2 during short hovering events (<1.5 s) was 19.0 ml g⁻¹ h⁻¹ (1.8 W) in 16-g Choeronycteris, which was not significantly different from a previous, indirect estimate of the cost of level forward flight (2.1 W, Winter and von Helversen 1998). Our estimates suggest that power input during hovering flight P _h (W) increased with body mass M (kg) within 13–18-g Choeronycteris (n = 4) as P _h  = 3544 (±2057 SE) M ^{1.76 (±0.21 SE)} and between different glossophagine bat species (n = 3) as P _h  = 128 (±2.4 SE) M ^{0.95 (±0.034 SE)}. The slopes of three scaling functions for flight power (hovering, level forward flight at intermediate speed and submaximal flight power) indicate that: 1. The relationship between flight power to flight speed may change with body mass in the 6–30-g bats from a J- towards a U-shaped curve. 2. A metabolic constraint (hovering flight power equal maximal flight power) may influence the upper size limit of 30–35 g for this group of flower specialists. Mass-specific power input (W kg⁻¹) during hovering flight appeared constant with regard to body size (for the mass ranges considered), but differed significantly (P < 0.001) between groups. Group means were 393 W kg⁻¹ (sphingid moths), 261 W kg⁻¹ (hummingbirds) and 159 W kg⁻¹ (glossophagine bats). Thus, glossophagine bats expend the least metabolic power per unit of body mass supported during hovering flight. At a metabolic power input of 1.1 W a glossophagine bat can generate the lift forces necessary for balancing 7 g against gravitation, whereas a hummingbird can support 4 g and a sphingid moth only 3 g of body mass with the same amount of metabolic energy. These differences in power input were not fully explained by differences in induced power output estimated from Rankine-Froude momentum-jet theory. Accepted: 10 November 1998     

Chemotactic collapse for the Keller-Segel model

 This work is concerned with the system (S) {u _t =Δu − χ∇ (u∇v) for x∈Ω, t>0Γ v _t =Δv+(u−1) for x∈Ω, t>0 where Γ, χ are positive constants and Ω is a bounded and smooth open set in ℝ². On the boundary ∂Ω, we impose no-flux conditions: (N) ∂u∂n =∂v∂n =0 for x∈∂ Ω, t>0 Problem (S), (N) is a classical model to describe chemotaxis corresponding to a species of concentration u(x, t) which tends to aggregate towards high concentrations of a chemical that the species releases. When completed with suitable initial values at t=0 for u(x, t), v(x, t), the problem under consideration is known to be well posed, locally in time. By means of matched asymptotic expansions techniques, we show here that there exist radial solutions exhibiting chemotactic collapse. By this we mean that u(r, t) →Aδ(y) as t→T for some T<∞, where A is the total concentration of the species. Received 9 March 1995; received in revised form 25 December 1995     

Relationship between maximal oxygen uptake on different ergometers, lean arm volume and strength in paraplegic subjects

The present experiment was designed to study the importance of strength and muscle mass as factors limiting maximal oxygen uptake (V˙O_{2 max} ) in wheelchair subjects. Thirteen paraplegic subjects [mean age 29.8 (8.7) years] were studied during continuous incremental exercises until exhaustion on an arm-cranking ergometer (AC), a wheelchair ergometer (WE) and motor-driven treadmill (TM). Lean arm volume (LAV) was estimated using an anthropometric method based upon the measurement of various circumferences of the arm and forearm. Maximal strength (MVF) was measured while pushing on the rim of the wheelchair for three positions of the hand on the rim (−30°, 0° and +30°). The results indicate that paraplegic subjects reached a similar V˙O_{2 max} [1.23 (0.34) l · min⁻¹, 1.25 (0.38) l · min⁻¹, 1.22 (0.18) l · min⁻¹ for AC, TM and WE, respectively] and V˙O_{2 max} /body mass [19.7 (5.2) ml · min⁻¹ · kg⁻¹, 19.5 (6.14) ml · min⁻¹ · kg⁻¹, 19.18 (4.27) ml · min⁻¹ · kg⁻¹ for AC, TM and WE, respectively on the three ergometers. Maximal heart rate f _{c max} during the last minute of AC (173 (17) beats · min⁻¹], TM [168 (14) beats · min⁻¹], and WE [165 (16) beats · min⁻¹], were correlated, but f _{c max} was significantly higher for AC than for TM (P<0.03). There were significant correlations between MVF and LAV (P<0.001) and between the MVF data obtained at different angles of the hand on the rim [311.9 (90.1) N, 313.2 (81.2) N, 257.1 (71) N, at −30°, 0° and +30°, respectively]. There was no correlation between V˙O_{2 max} and LAV or MVF. The relatively low values of f _{c max} suggest that V˙O_{2 max} was, at least in part, limited by local aerobic factors instead of central cardiovascular factors. On the other hand, the lack of a significant correlation between V˙O_{2 max} and MVF or muscle mass was not in favour of muscle strength being the main factor limiting V˙O_{2 max} in our subjects. Accepted: 31 January 1997     

Detection of the change point in oxygen uptake during an incremental exercise test using recursive residuals: relationship to the plasma lactate accumulation and blood acid base balance

The purpose of this study was to develop a method to determine the power output at which oxygen uptake (V˙O₂) during an incremental exercise test begins to rise non-linearly. A group of 26 healthy non-smoking men [mean age 22.1 (SD 1.4) years, body mass 73.6 (SD 7.4) kg, height 179.4 (SD 7.5) cm, maximal oxygen uptake (V˙O_2max) 3.726 (SD 0.363) l · min⁻¹], experienced in laboratory tests, were the subjects in this study. They performed an incremental exercise test on a cycle ergometer at a pedalling rate of 70 rev · min⁻¹. The test started at a power output of 30 W, followed by increases amounting to 30 W every 3 min. At 5 min prior to the first exercise intensity, at the end of each stage of exercise protocol, blood samples (1 ml each) were taken from an antecubital vein. The samples were analysed for plasma lactate concentration [La]_pl, partial pressure of O₂ and CO₂ and hydrogen ion concentration [H⁺]_b. The lactate threshold (LT) in this study was defined as the highest power output above which [La⁻]_pl showed a sustained increase of more than 0.5 mmol · l⁻¹ · step⁻¹. The V˙O₂ was measured breath-by-breath. In the analysis of the change point (CP) of V˙O₂ during the incremental exercise test, a two-phase model was assumed for the 3rd-min-data of each step of the test: X _i =at _i +b+ɛ _i for i=1,2,…,T, and E(X _i )>at _i +b for i =T+1,…,n, where X ₁, … , X _n are independent and ɛ _i ∼N(0,σ²). In the first phase, a linear relationship between V˙O₂ and power output was assumed, whereas in the second phase an additional increase in V˙O₂ above the values expected from the linear model was allowed. The power output at which the first phase ended was called the change point in oxygen uptake (CP-V˙O₂). The identification of the model consisted of two steps: testing for the existence of CP and estimating its location. Both procedures were based on suitably normalised recursive residuals. We showed that in 25 out of 26 subjects it was possible to determine the CP-O₂ as described in our model. The power output at CP-V˙O₂ amounted to 136.8 (SD 31.3) W. It was only 11 W – non significantly – higher than the power output corresponding to LT. The V˙O₂ at CP-V˙O₂ amounted to 1.828 (SD 0.356) l · min⁻¹ was [48.9 (SD 7.9)% V˙O_{2 max} ]. The [La⁻]_pl at CP-V˙O₂, amounting to 2.57 (SD 0.69) mmol · l⁻¹ was significantly elevated (P<0.01) above the resting level [1.85 (SD 0.46) mmol · l⁻¹], however the [H⁺]_b at CP-V˙O₂ amounting to 45.1 (SD 3.0) nmol · l⁻¹, was not significantly different from the values at rest which amounted to 44.14 (SD 2.79) nmol · l⁻¹. An increase of power output of 30 W above CP-V˙O₂ was accompanied by a significant increase in [H⁺]_b above the resting level (P=0.03). Accepted: 25 March 1998     

BACE and γ-Secretase Characterization and Their Sorting as Therapeutic Targets to Reduce Amyloidogenesis

Secretases are named for enzymes processing amyloid precursor protein (APP), a prototypic type-1 membrane protein. This led directly to discovery of novel Aspartyl proteases (β-secretases or BACE), a tetramer complex γ-secretase (γ-SC) containing presenilins, nicastrin, aph-1 and pen-2, and a new role for metalloprotease(s) of the ADAM family as a α-secretases. Recent advances in defining pathways that mediate endosomal-lysosomal-autophagic-exosomal trafficking now provide targets for new drugs to attenuate abnormal production of fibril forming products characteristic of AD. A key to success includes not only characterization of relevant secretases but mechanisms for sorting and transport of key metabolites to abnormal vesicles or sites for assembly of fibrils. New developments we highlight include an important role for an ‘early recycling endosome’ coated in retromer complex containing lipoprotein receptor LRP-II (SorLA) for switching APP to a non-amyloidogenic pathway for α-secretases processing, or to shuttle APP to a ‘late endosome compartment’ to form Aβ or AICD. LRP11 (SorLA) is of particular importance since it decreases in sporadic AD whose etiology otherwise is unknown.     

A <Emphasis Type="Italic">FRUITFULL-like</Emphasis> gene is associated with genetic variation for fruit flesh firmness in apple (<Emphasis Type="Italic">Malus domestica</Emphasis> Borkh.)

The FRUITFULL (FUL) and SHATTERPROOF (SHP) genes are involved in regulating fruit development and dehiscence in Arabidopsis. We tested the hypothesis that this class of genes are also involved in regulating the development of fleshy fruits, by exploring genetic and phenotypic variation within the apple (Malus domestica) gene pool. We isolated and characterised the genomic sequences of two candidate orthologous FUL-like genes, MdMADS2.1 and MdMADS2.2. These were mapped using the reference population ‘Prima x Fiesta’ to loci on Malus linkage groups LG14 and LG06, respectively. An additional MADS-box gene, MdMADS14, shares high amino acid identity with the Arabidopsis SHATTERPROOF1/2 genes and was mapped to Malus linkage group LG09. Association analysis between quantitative fruit flesh firmness estimates of ‘Prima x Fiesta’ progeny and the MdMADS2.1, MdMADS2.2 and MdMADS14 loci was carried out using a mixed model analysis of variance. This revealed a significant association (P < 0.01) between MdMADS2.1 and fruit flesh firmness. Further evidence for the association between MdMADS2.1 and fruit flesh firmness was obtained using a case–control population-based genetic association approach. For this, a polymorphic repeat, (AT)_n, in the 3′ UTR of MdMADS2.1 was used as a locus-specific marker to screen 168 apple accessions for which historical assessments of fruit texture attributes were available. This analysis revealed a significant association between the MdMADS2.1 and fruit flesh firmness at both allelic (χ ² = 34, df = 9, P < 0.001) and genotypic (χ ² = 57, df = 32, P < 0.01) levels.     

High-resolution mapping of a linkage group on mouse chromosome 8 conserved on human chromosome 16Q

We have performed a high-resolution linkage analysis for the conserved segment on distal mouse Chromosome (Chr) 8 that is homologous to human Chr 16q. The interspecific backcross used involved M. m. molossinus and an M. m. domesticus line congenic for an M. spretus segment from Chr 8 flanked by phenotypic markers Os (oligosyndactyly) and e, a coat colormarker. From a total of 682 N₂ progeny, the 191 animals revealing a recombination event between these phenotypic markers were typed for 23 internal loci. The following locus order with distances in cM was obtained: (centromere)–Os–4.1–Mmp2–0.2–Ces1,Es1, Es22–1.2–Mt1,D8Mit15–2.2–Got2, D8Mit11–3.7–Es30–0.3–Es2, Es7–0.9–Ctra1,Lcat–0.3–Cdh1, Cadp, Nmor1, D8Mit12–0.2–Mov34–2.5–Hp,Tat–0.2–Zfp4–1.6–Zfp1,Ctrb–10.9–e. In a separate interspecific cross involving 62 meioses, Dpep1 was mapped together with Aprt and Cdh3 at 12.9 cM distal to Hp, Tat, to the vicinity of e. Our data give locus order for markers not previously resolved, add Mmp2 and Dpep1 as new markers on mouse Chr 8, and indicate that Ctra1 is the mouse homolog for human CTRL. Comparison of the order of 17 mouse loci with that of their human homologs reveals that locus order is well conserved and that the conserved segment in the human apparently spans the whole long arm of Chr 16. Received: 30 July 1996 / Accepted: 15 November 1996     

Comparison of the effects of temperature and water activity on growth rate of food spoilage moulds

The influence of temperature (T) and water activity (a _w) on the growth rate (μ) of seven moulds (Alternaria alternata, Aspergillus flavus, Cladosporium cladosporioides, Mucor racemosus, Penicillium chrysogenum, Rhizopus oryzae and Trichoderma harzianum) was assessed in suboptimal conditions. Firstly, the dependence of fungal growth on temperature, at a _w 0.99, was modelled through an approach described previously for bacteria. A dimensionless growth rate variable: μ _dimα=μ/μ _optα depended on the following normalised temperature: T _dim=(T−T _min)/(T _opt− T _min) according to a power function: μ _dimα=[T _dim] ^α , where α was an exponent to be estimated. Secondly, the same approach was used to describe the influence of a _w on fungal growth, at the respective optimum temperatures for each mould. Similarly, μ _dimβ=μ/μ _optβ depended on the following normalised water activity: a _wdim=(a _w−a _wmin)/(a _wopt−a _wmin) according to a power function: μ _dimβ=[a _wdim]^β. Results show: (i) for each mould, the α-value is significantly less than the β-value, confirming that water activity has a greater influence than temperature on fungal development; (ii) the α-values and the β-values depend on the mould; (iii) the α-value is less than 1 for the mesophilic mould A. flavus, whereas the other moulds are characterised by higher α-values ranging from 1.10 to 1.54; (iv) the mesophilic A. flavus exhibits a low β-value, 1.50, compared to the hydrophilic T. harzianum, β=2.44, while β-values are within the range (1.71–2.37) for the other moulds. Journal of Industrial Microbiology & Biotechnology (2002) 28, 311–315 DOI: 10.1038/sj/jim/7000248 Received 27 June 2001/ Accepted in revised form 04 February 2002     

The effect of a thiamin derivative on exercise performance

The purpose of this study was to investigate the effect of a thiamin derivative, thiamin tetrahydrofurfuryl disulfide (TTFD), on oxygen uptake (˙VO₂), lactate accumulation and cycling performance during exercise to exhaustion. Using a randomized, double-blind, cross-over design with a 10-day washout between trials, 14 subjects ingested either 1 g · day⁻¹ of TTFD or a placebo (PL) for 4 days. On day 3, subjects performed a progressive exercise test to exhaustion on a cycle ergometer for the determination of ˙VO_2submax, ˙VO_2peak, lactate concentration ([La⁻ ]), lactate threshold (Th_La) and heart rate ( f _c). On day 4, subjects performed a maximal 2000-m time trial on a cycle ergometer. A one-way analysis of variance (ANOVA) with repeated measures was used to determine significant differences between trials. There were no significant differences detected between trials for serial measures of ˙VO_2submax, [La⁻] or f _c. Likewise, ˙VO_2peak [PL 4.06 (0.19) TTFD 4.12 (0.19) l · min⁻¹, P = 0.83], Th_La [PL 2.47 (0.17), TTFD 2.43 (0.16) l · min⁻¹, P = 0.86] and 2000-m performance time [PL 204.5 (5.5), TTFD 200.9 (4.3) s, P = 0.61] were not significantly different between trials. The results of this study suggest that thiamin derivative supplementation does not influence high-intensity exercise performance. Accepted: 19 December 1996     

Transient oxygen uptake response to exercise characterizes functional capacity of the cardiocirculatory system in patients with chronic heart failure: a random stimulus approach

The transient response of oxygen uptake (V˙O₂) to submaximal exercise, known to be abnormal in patients with cardiovascular disorders, can be useful in assessing the functional status of the cardiocirculatory system, however, a method for evaluating it accurately has not yet been established. As an alternative approach to the conventional test at constant exercise intensity, we applied a random stimulus technique that has been shown to provide relatively noise immune responses of system being investigated. In 27 patients with heart failure and 24 age-matched control subjects, we imposed cycle exercise at 50 W intermittently according to a pseudo-random binary (exercise-rest) sequence, while measuring breath-by-breath V˙O₂. After determining the transfer function relating exercise intensity (W˙) to V˙O₂ and attenuating the high frequency ranges (>6 exercise-rest cycles · min⁻¹), we computed the high resolution band-limited (0–6 cycles · min⁻¹) V˙O₂ response (0–120 s) to a hypothetical step exercise. The V˙O₂ response showed a longer time constant in the patients than in the control subjects [47 (SD 37) and 31 (SD 8) s, respectively, P < 0.05]. Furthermore, the amplitude of the V˙O₂ response after the initial response was shown to be significantly smaller in the patients than in the control subjects [176 (SD 50) and 267 (SD 54) ml · min⁻¹ at 120 s]. The average amplitude over 120 s correlated well with peak V˙O₂ (r = 0.73) and ΔV˙O₂/ΔW˙ (r = 0.70), both of which are well-established indexes of exercise tolerance. The data indicated that our band-limited V˙O₂ step response using random exercise was more markedly attenuated and delayed in the patients with heart failure than in the normal controls and that it could be useful in quantifying the overall functional status of the cardiocirculatory system. Accepted: 6 January 1998     

O-polysaccharide structure in serogroup I azospirilla

Lipopolysaccharides (LPS) and O-specific polysaccharides (OPS) were obtained from the outer membrane of four Azospirillum strains previously assigned to serogroup I based on the serological affinity revealed by the antibodies (AB) to the LPS of A. brasilense Sp245. Investigation, including determination of monosaccharide composition, methylation analysis, and one- and two-dimensional NMR spectroscopy, was carried out to determine the OPS structure. The OPSs of A. brasilense Sp107 and S27 and of A. lipoferum RG20a were found to have an identical structure of repeating units represented by a linear penta-D-rhamnan, as was previously described for the OPSs of A. brasilense Sp245 and SR75. The OPS of A. brasilense SR15 was found to consist of tetrasaccharide repeating units of the following structure: → 2)-α-D-Rhap-(1 → 2)-β-D-Rhap-(1 → 3)-α-D-Rhap-(1 → 2)-α-D-Rhap-(1 →. An opine compound, N^δ-(1-carboxyethyl)-ornithine, closely associated with the LPS of A. brasilense SR15, was identified in azospirilla for the first time. The presence of a 6-deoxisugar (D-rhamnose) in the OPS structure was shown to be the chemical basis of the serological similarity and the reason for classification of these strains within the serogroup I.     

Bounds on the total particle number for species governed by reaction-diffusion equations in the infinite spatial domain

Differential inequality methods are developed for establishing upper and lower bounds on the total particle numberN(t)=∫θ(x,t) d³ x associated with solutions to nonlinear reaction-diffusion equations of the form ∂θ/∂t=D∇²θ+fθ-gθ ⁿ⁺¹ , whereD(>0),n(>0),f andg are constant parameters. If finite in a neighborhood oft=0,N(t) is bounded below for allt≥0 by a certain derived function oft for equations withg≥0. An upper bound onN(t) is obtained for equations withn=1,f<0 andg<0. These results provide general preservation and extinction criteria for the total particle number.     

A method for numbering binary rooted and unrooted phylogenies and their hypothetical taxonomic units

A set of 2n−2 relations (edges) and a set ofn−1 hypothetical taxonomic units (HTUs) derive from the estimation of a binary phylogeny of a set ofn operational taxonomic units (OTUs). We propose an easy way for numbering thesen−1 hypothetical taxonomic units, as well as for then−2 interior points of an unrooted binary phylogeny. We also present an alternative method to the one proposed by Rohlf (Bull. math. Biol. 45, 33–40, 1983) for numbering the π _i=1 ⁿ (2i−3) possible rooted binary phylogenies and the π _i=1 ⁿ⁻¹ (2i−3) possible unrooted binary phylogenies conerning a set ofn operational taxonomic units. An illustrative example of the method is presented. It is hoped that some studies in phylogenetics will become more accessible, from the viewpoint of computational economy, by the use of this method.     

Improving rice yield and quality by QTL pyramiding

To facilitate marker-assisted transfer of desirable genes for improvement of yield traits, we used a set of backcross recombinant inbred lines (BRIL) derived from two elite parental lines, ‘Zhenshan97’ and ‘93-11’, to resolve a quantitative trait loci (QTL) cluster for heading date and yield-related traits in rice. Four main-effect QTL (qHD6.1, qHD6.2, qHD7, and qHD8) and four epistatic QTL affecting heading date in the BRIL were detected in two experimental trials. The major QTL (qHD8) was confirmed in three heterogeneous inbred families (HIF) that segregated for this target region, and narrowed down to a 20-kb segment in a large HIF-derived population. qHD8 was found to interact with qHD7 and had a pleiotropic effect responsible for heading date and yield components. To test usability of the identified QTL in rice improvement, we further developed near-isogenic lines (NIL) containing one or more target genes by marker-assisted transfer of ‘93-11’ alleles at qHD8, qHD7, and qHD6.1, and the GS3 gene for grain size into ‘Zhenshan97’. The pyramid line NIL(qHD8 + GS3) had higher yield potential, longer grains, and a more suitable heading date than ‘Zhenshan97’. Comparison of the NIL showed existence of epistasis between alleles at different loci and background effect on qHD8, which are very important for pyramiding of desirable alleles at the target QTL. These results will be particularly useful not only to understand the genetic basis of yield-related traits but also to improve the efficiency of marker-assisted selection for favorable loci in rice breeding programs.     

Validation of density functional modeling protocols on experimental bis(μ-oxo)/μ-η<Superscript>2</Superscript>:η<Superscript>2</Superscript>-peroxo dicopper equilibria

The bis(μ-oxo)/μ-η²:η²-peroxo equilibria for seven supported Cu₂O₂ cores were studied with different hybrid and nonhybrid density functional theory models, namely, BLYP, mPWPW, TPSS, TPSSh, B3LYP, mPW1PW, and MPW1K. Supporting ligands 3,3′-iminobis(N,N-dimethylpropylamine), N,N,N′,N′,N″-pentamethyldipropylenetriamine, N-[2-(pyridin-2-yl)ethyl]-N,N,N′-trimethylpropane-1,3-diamine, bis[2-(2-pyridin-2-yl)ethyl]methylamine, bis[2-(4-methoxy-2-pyridin-2-yl)ethyl]methylamine, bis[2-(4-N,N-dimethylamino-2-pyridin-2-yl)ethyl]methylamine, and 1,4,7-triisopropyl-1,4,7-triazacyclononane were chosen on the basis of the availability of experimental data for comparison. Density functionals were examined with respect to their ability accurately to reproduce experimental properties, including, in particular, geometries and relative energies for the bis(μ-oxo) and side-on peroxo forms. While geometries from both hybrid and nonhybrid functionals were in good agreement with experiment, the incorporation of Hartree–Fock (HF) exchange in hybrid density functionals was found to have a large, degrading effect on predicted relative isomer energies. Specifically, hybrid functionals predicted the μ-η²:η²-peroxo isomer to be too stable by roughly 5–10 kcal mol⁻¹ for each 10% of HF exchange incorporated into the model. Continuum solvation calculations predict electrostatic effects to favor bis(μ-oxo) isomers by 1–4 kcal mol⁻¹ depending on ligand size, with larger ligands having smaller differential solvation effects. Analysis of computed molecular partition functions suggests that nonzero measured entropies of isomerization are likely to be primarily associated with interactions between molecular solutes and their first solvation shell. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Contributions of C3 and C4 plants to higher trophic levels in an Amazonian savanna

We studied the energy flow from C₃ and C₄ plants to higher trophic levels in a central Amazonian savanna by comparing the carbon stable-isotope ratios of potential food plants to the isotope ratios of species of different consumer groups. All C₄ plants encountered in our study area were grasses and all C₃ plants were bushes, shrubs or vines. Differences in δ¹³C ratios among bushes (xˉ = −30.8, SD = 1.2), vines (xˉ = −30.7, SD = 0.46) and trees (xˉ = −29.7, SD = 1.5) were small. However the mean δ¹³C ratio of dicotyledonous plants (xˉ = −30.4, SD = 1.3) was much more negative than that of the most common grasses (xˉ = −13.4, SD = 0.27). The insect primary consumers had δ¹³C ratios which ranged from a mean of −29.5 (SD = 0.47) for the grasshopper Tropidacris collaris to a mean of −14.7 (SD = 0.56) for a termite (Nasutitermes sp.), a range similar to that of the vegetation. However, the common insectivorous and omnivorous vertebrates had intermediate values for δ¹³C, indicating that carbon from different autotrophic sources mixes rapidly as it moves up the food chain. Despite this mixing, the frogs and lizards generally had higher values of δ¹³C (xˉ = −21.7, SD = 1.6; xˉ = −21.9, SD = 1.8, respectively) than the birds (xˉ = −24.8, SD = 1.8) and the only species of mammal resident in the savanna (xˉ = −25.4), indicating that they are generally more dependent on, or more able to utilise, food chains based on C₄ grasses. Received: 7 May 1998 / Accepted: 30 November 1998     

CCN2 (Connective Tissue Growth Factor) is essential for extracellular matrix production and integrin signaling in chondrocytes

The matricellular protein CCN2 (Connective Tissue Growth Factor; CTGF) is an essential mediator of ECM composition, as revealed through analysis of Ccn2 deficient mice. These die at birth due to complications arising from impaired endochondral ossification. However, the mechanism(s) by which CCN2 mediates its effects in cartilage are unclear. We investigated these mechanisms using Ccn2 ^−/− chondrocytes. Expression of type II collagen and aggrecan were decreased in Ccn2 ^−/− chondrocytes, confirming a defect in ECM production. Ccn2 ^−/− chondrocytes also exhibited impaired DNA synthesis and reduced adhesion to fibronectin. This latter defect is associated with decreased expression of α5 integrin. Moreover, CCN2 can bind to integrin α5β1 in chondrocytes and can stimulate increased expression of integrin α5. Consistent with an essential role for CCN2 as a ligand for integrins, immunofluorescence and Western blot analysis revealed that levels of focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK)1/2 phosphorylation were reduced in Ccn2 ^−/− chondrocytes. These findings argue that CCN2 exerts major effects in chondrocytes through its ability to (1) regulate ECM production and integrin α5 expression, (2) engage integrins and (3) activate integrin-mediated signaling pathways.     

Identification of protein kinase disruptions as suppressors of the calcium sensitivity of S. cerevisiae Δptp2 Δmsg5 protein phosphatase double disruptant

The double disruptant of the S. cerevisiae protein phosphatase (PPase) genes, PTP2 (phosphotyrosine-specific PPase) and MSG5 (phosphotyrosine and phosphothreonine/serine-PPase) causes calcium-sensitive growth (Ca^s). Previous study using Fluorescent-activated cell sorting (FACS) analysis showed that this growth defect with calcium occurs at G1–S transition in the cell cycle. We discovered that six non-essential protein kinase (PKase) disruptions (Δbck1, Δmkk1, Δslt2/Δmpk1, Δmck1, Δssk2 and Δyak1) suppressed the Ca^s-phenotype of the Δptp2 Δmsg5 double disruptant. Bck1p, Mkk1p and Slt2p are components of the mitogen-activated protein kinase (MAPK) cascade of cell wall integrity pathway (Slt2 pathway), and Mck1p is its down regulator. Ssk2p is the MAPK kinase kinase of the high-osmolarity glycerol (HOG) pathway, while Yak1p is a negative regulator for the cAMP-dependent PKA pathway. FACS analysis revealed that only the disruption of Δssk2 and Δyak1 but not Δbck1, Δmkk1, Δslt2 and Δmck1 was able to suppress the delayed G1–S transition, suggesting that suppression of the growth defect is not always accompanied by suppression of the G1–S transition delay. The discovery of these PKases as suppressors revealed that in addition to the previously anticipated Slt2 pathway, HOG, Yak1p and Mck1p regulatory pathways may also be involved in the calcium sensitivity of the Δptp2 Δmsg5 double disruptant.