Effects of shell morphological traits on the weight traits of Manila clam (Ruditapes philippinarum)

The shell length, height, and width, live body weight, and edible tissue weight of Manila clam of 1, 2, and 3 years of age were measured, and their correlation coefficients were calculated. The shell morphological traits were used as independent variables, and live body weight or edible tissue weigh used as a dependent variable for calculating the path coefficients, correlation index and determination coefficients. The results showed that the correlation coefficients between each shell morphological trait and the live body weight or edible tissue weight were all highly significant (P < 0. 01). The shell height at 1-year old clams was highly correlated with the live body weight and edible tissue weight. The shell width of 2- to 3-year-old clams was strongly associated with the live body weight, while the shell length was closely linked to the edible tissue weight. The results of coefficients of determination for the morphological traits against weight traits agreed well with the results of path analysis. The correlation indices for all morphological traits against weight traits were approximately the same as determination coefficients regardless of clam age. The correlation indices (R²) of morphological traits against the live body weight of clams of all ages and edible tissue weight of 1-year-old clams were larger than 0.85, but R² of morphological traits against the edible tissue weight of 2- and 3-year-old clams was smaller than 0.85, indicating that some other factors might be associated with the edible tissue weight of 2- and 3-year-old clams. Multiple regression equations were obtained to estimate shell length X₁ (cm), shell height X₂ (cm), shell width X₃ (cm) against live body weight Y (g), edible tissue weight Z (g): for 1-year-old clams: Y = ?4.317 + 0.18X₁ + 0.147X₂, (X₁ < 0.01, X₂ < 0.01), Z = ?1.011 + 0.095X₂, (X₂ < 0.01); for 2-year-old clams: Y = ?15.119 + 0.249X₁ + 0.176X₂ + 0.688X₃, (X₁ < 0.01, X₃ < 0.01), Z = ?4.248 + 0.198X₁, (X₁ < 0.05, X₃ < 0.01); and for 3-year-old clams: Y = ?25.013 + 0.415X₁ + 1.184X₃, (X₁ < 0.01, X₃ < 0.01), Z = ?7.082 + 0.119X₁ + 0.332X₃, (X₁ < 0.05, X₃ < 0.01).     

Maitotoxin and P2Z/P2X7 purinergic receptor stimulation activate a common cytolytic pore

The effects ofmaitotoxin (MTX) on plasmalemma permeability are similar to thosecaused by stimulation of P2Z/P2X₇ionotropic receptors, suggesting that1) MTX directly activatesP2Z/P2X₇ receptors or2) MTX andP2Z/P2X₇ receptor stimulationactivate a common cytolytic pore. To distinguish between these twopossibilities, the effect of MTX was examined in1) THP-1 monocytic cells before andafter treatment with lipopolysaccharide and interferon-, a maneuverknown to upregulate P2Z/P2X₇receptor, 2) wild-type HEK cells andHEK cells stably expressing theP2Z/P2X₇ receptor, and3) BW5147.3 lymphoma cells, a cellline that expresses functional P2Z/P2X₇ channels that are poorlylinked to pore formation. In control THP-1 monocytes, addition of MTXproduced a biphasic increase in the cytosolic freeCa²⁺ concentration([Ca²⁺]_i);the initial increase reflects MTX-inducedCa²⁺ influx, whereas the secondphase correlates in time with the appearance of large pores and theuptake of ethidium. MTX produced comparable increases in[Ca²⁺]_iand ethidium uptake in THP-1 monocytes overexpressing theP2Z/P2X₇ receptor. In bothwild-type HEK and HEK cells stably expressing theP2Z/P2X₇ receptor, MTX-inducedincreases in[Ca²⁺]_iand ethidium uptake were virtually identical. The response of BW5147.3cells to concentrations of MTX that produced large increases in[Ca²⁺]_ihad no effect on ethidium uptake. In both THP-1 and HEK cells, MTX- andBz-ATP-induced pores activate with similar kinetics and exhibit similarsize exclusion. Last, MTX-induced pore formation, but not channelactivation, is greatly attenuated by reducing the temperature to22°C, a characteristic shared by theP2Z/P2X₇-induced pore. Together,the results demonstrate that, although MTX activates channels that aredistinct from those activated byP2Z/P2X₇ receptor stimulation, thecytolytic/oncotic pores activated by MTX- and Bz-ATP are indistinguishable.

     

Some Experimental and Theoretical Observations Concerning Mass Flow in the Vascular Bundles of Heracleum

The theory and practice of applying the thermodynamics of irreversibleprocesses to mass-flow theories is presented. Onsager coefficientswere measured on cut and uncut phloem and cut xylem strandsof Heracleum muntegazzimum. In 0.3 N sucrose + 1 mN KC1 theyare as follows. In phloem, L_EE = 5 ? 10–⁴ mho cm^–1,L_pE = 9 ? 10^–6 cm³ s^–1 cm^–2 volt^–1 cm,and L_PP = 0.16 cm³ s^–1 cm^–2 (J cm^–3)^–1cm. In uncut phloem strands L_EE is about 1 ? 10^–3 mhocm^–1. In xylem in 2 x 10^–3 N KCI, L_pp = 50 to 225,L_PE = 2 ? 10^–4, and L^EE = 4 ? 10^–3. The measurementsare tentative since the blockage of the sieve plates is an interferingfactor, but if they are valid they lead to the conclusion thatneither a pressure-flow nor an electro-kinetic mechanism envisaginga ‘long distance’ current pathway can be the majormotive ‘force’ for transport in mature phloem. Measurementsof biopotentials along conducting but laterally detached phloembundles of Heracleum suggest, nevertheless, that there may bea small electro-osmotic component of at least 0.1 mV cm^–1endogenous in the phloem.     

The effects of capture, net retention and preservation upon lengths of larval and juvenile bass, Dicentrarchus labrax (L.)

Relationships between live and preserved lengths of larval and juvenile bass, Dicentrarchus labrax , subjected to simulated capture, net retention and preservation were investigated. Bass larvae and juveniles shrank during the period of net retention following death. Preserved lengths of larvae, but not of juveniles, decreased significantly when increased periods of net retention preceded preservation. The time which larvae or juveniles remained in 4% formaldehyde in distilled water buffered with 3gl⁻¹ sodium acetate trihydrate or in 70% ethanol in distilled water neutralized with 1gl⁻¹ calcium carbonate powder, had no significant effect upon preserved length. Appropriate data were pooled to calculate transformation factors for estimating live from preserved length. Shrinkage phenomena, and their effects, are discussed. It is suggested that larval bass captured and preserved during standard ichthyoplankton surveys are unsuitable for determination of live length.     

Shrinkage of Prochilodus lineatus (Valenciennes, 1847) larvae preserved in either ethyl‐alcohol or formalin in relation to their developmental stage and feeding condition

The effects of preservation in 95% ethyl‐alcohol and 5% formalin were analysed for 3 months on standard length of Prochilodus lineatus larvae from hatching to the end of the flexion process. Unyolked stages were raised under two feeding regimes: unfed and daily fed. All developmental stages that were preserved in formalin as well as the yolked and flexion‐postflexion larvae stored in alcohol shrank significantly (2–6%). In contrast, unyolked preflexion larvae showed a slight but significant enlargement after storage in alcohol (1%). Shrinkage of preflexion stages was 2.5% higher when stored in formalin, while both preservative agents caused similar shrinkage in flexion‐postflexion larvae (ca. 3%). Shrinkage levels after storage in alcohol were dependent on live length, decreasing or increasing with increasing length in yolked and flexion‐postflexion larvae, respectively. The feeding regime did not affect length changes after preservation in either preservative agent.     

Positive Association Among Three Binary Variables and Cross-Product Ratios

We show that, when the three-way association level among thethree binary variables, X, U₁ and U₂ is fixed, D_P = pr(X = 1¦U₁= 1) – pr(X = 1¦U₁ = 0) increases as the cross-productratio of U₁ and U₂ increases under the assumption that X ispositively associated with U₁ and U₂. We then discuss some implicationsof this property.     

Mechanical and metabolic determination of VO2 and fatigue during repetitive isometric contractions in situ

Repetitiveisometric tetanic contractions (1/s) of the caninegastrocnemius-plantaris muscle were studied either at optimal length(L_o) or shortlength (L_s;~0.9 · L_o),to determine the effects of initial length on mechanical and metabolicperformance in situ. Respective averages of mechanical and metabolicvariables were(L_o vs.L_s, allP < 0.05) passive tension (preload) = 55 vs. 6 g/g, maximal active tetanic tension(P_o) = 544 vs. 174 (0.38 · P_o)g/g, maximal blood flow () = 2.0 vs. 1.4 ml · min¹ · g¹,and maximal oxygen uptake(O₂) = 12 vs. 9 µmol · min¹ · g¹.Tension at L_odecreased to0.64 · P_o over20 min of repetitive contractions, demonstrating fatigue; there were nosignificant changes in tension atL_s. In separatemuscles contracting atL_o, was set to that measured atL_s (1.1 ml · min¹ · g¹),resulting in decreased O₂(7 µmol · min¹ · g¹),and rapid fatigue, to0.44 · P_o. Thesedata demonstrate that 1)muscles at L_ohave higher andO₂ values than those at L_s;2) fatigue occurs atL_o with highO₂, adjusting metabolic demand (tension output) to match supply; and3) the lack of fatigue atL_s with lowertension, , andO₂ suggestsadequate matching of metabolic demand, set low by shortmuscle length, with supply optimized by low preload. Thesedifferences in tension andO₂ betweenL_o andL_s groupsindicate that muscles contracting isometrically at initial lengthsshorter than L_oare working under submaximal conditions.

     

利用人工合成性信息素诱捕器诱捕印度谷螟的影响因素分析

采用自行设计式及仿制圆筒式诱捕器,以人工合成性信息素(Z,E)-9,12-tetradecadienyl acetate (简称TDA) 为引诱源在实验室条件下对影响诱捕器诱捕印度谷螟Plodia interpunctella效果的几个因素进行分析测定。多元线性回归分析结果表明：日平均温度在18.5～26.2℃,人工合成性信息素TDA散发日数9～37天,温度(X₁)、TDA散发日数(X₂)、当日释放蛾(雄)量(X₃)、累计2日释放蛾量(X₄)、累计3日释放蛾量(X₅)等5个因素与每日诱捕蛾量间存在着相关关系。对5个因素进行逐步回归分析和筛选,得出线性回归方程：Y=-27.31+1.37X₁+0.28X₃,回归系数R（0.90）>R_0.01(n-2,0.63)。统计分析结果表明：日平均温度(X₁)、当日释放蛾量(X₃)与诱蛾量(Y)之间呈显著线性相关关系。卡方测验表明预测值与实测值之间差异不显著。     

环境因子对角倍蚜秋迁蚜生殖和雌性蚜发育的影响

研究了环境因子对角倍蚜Schlechtendalia chinensis (Bell) 秋迁蚜生殖和雌性蚜发育的影响。温、湿度单因子试验表明,秋迁蚜在26℃和80%RH条件下有最大生殖量;温、湿度对秋迁蚜生殖量的影响均符合开口向下的二次抛物线变化趋势,极端温、湿度会导致生殖量的下降。采用三元一次正交组合设计,研究了环境温度（X₁）、湿度（X₂）和光照强度（X₃）三因子不同水平组合对雌性蚜发育的影响,表明温度是影响发育历期的主要因子,其次是光照强度,最后是湿度。因此,适当高温、强光照条件可以加快雌性蚜发育;而适当高湿条件可以降低雌性蚜的发育速率而延长其发育历期。在人工培育角倍蚜生产中,创造有利于秋迁蚜生殖的温、湿度条件可以使秋迁蚜产下较多的越冬侨蚜;在适当降低温度、增加湿度的阴暗条件下贮留雌性蚜可以适当延长其发育,以使角倍蚜与盐肤木在物候上达到最佳吻合。     

影响叶螨磷酸酯酶活性的四因子数学模型

应用二次回归通用旋转组合设计,组建了影响叶螨磷酸酯酶（酸性和碱性）活性的四因子（缓冲液Ph值X₁、温浴时间X₂、反应温度X₃、底物浓度X₄）数学模型: Y_酸性=0.456380+0.107889X₂+0.069027X₃-0.026836X₁²-0.030794X₃², F=24.98,P<0.01;Y_碱性=0.267286-0.200736X₁+0.049541X₂+0.030930X₃-.049063X₁X₂+0.053585X₁²-0.049665X₂^2, F=57.68,P<0.01。结果表明,温浴时间是影响叶螨酸性磷酸酯酶活性的关键因子,在缓冲液pH 4.4、底物浓度8.5×10^-3 mol/L、42℃温浴40 min测得该酶活性最强。影响碱性磷酸酯酶活性的关键因子则是缓冲液pH值,pH 9.0、37℃恒温30 min、底物7.5×10^-3 mol/L的条件下,光密度值最大。两种酶的最大吸收峰波长为405 nm。     

Temperature Response of Early Foliar Expansion of Potato and Wheat

We studied the course of early leaf area expansion and specificleaf area (S_LA) in potato (Solanum tuberosum L.) and wheat (Triticumaestivum L.) genotypes and tested whether air temperature explainsdifferences in these courses within different environments.Such knowledge can be used to improve crop growth modelling.The relative rate of leaf area expansion (R_L) of potato andwheat decreased with thermal time, but was nearly linear upto a leaf area index (L) of 1.0. TheR_L (L < 1; mean: 17.9x 10^-3°C^-1 d^-1) of potato showed an interaction betweengenotype and environment, and varied with year. TheR_L (L <1; mean: 7.1 x 10^-3°C^-1 d^-1) of winter wheat was lower thanthat of spring wheat (mean: 10.9 x 10^-3°C^-1 d^-1), and bothvaried with year. S_LAof potato increased nearly linearly withthermal time from 5 to 15 m² kg^-1at 50% emergence, to 20 to25 m² kg^-1at 155°Cd, and then decreased slightly. The S_LAofboth winter and spring wheat began at 16 to 23 m² kg^-1and inmost cases increased slightly with thermal time. In potato,regression parameters of S_LAwith thermal time were affectedby environment (management conditions and year) and genotype;in wheat they were affected by environment (year and site).Treatment effects on R_Lof potato were not correlated with thoseon S_LA , and were only partly correlated for wheat. Thereforewe conclude that the early foliar expansion of potato is associatedwith a strong increase in S_LA , and not so for wheat. For bothcrops the course of early leaf area expansion and ofS_LA withair temperature is not robust over environments and genotypes.The consequences of these results for modelling are discussed.Copyright 2000 Annals of Botany Company Triticum aestivum, spring wheat, winter wheat, Solanum tuberosum, leaf area expansion, specific leaf area, early growth, genotype, environment, modelling     

Mechanical strain memory in airway smooth muscle

We investigated the effect of a singlerapid stretch on poststretch force and myosin phosphorylation in bovinetracheal smooth muscle. When unstimulated muscle strips were stretchedfrom suboptimal length to optimal length (L_o),poststretch steady-state force was not significantly different fromthat of unstretched control at L_o. However, whencarbachol-activated muscle strips were stretched from suboptimal lengthto L_o, poststretch force and myosin phosphorylation were lower than control and significantly correlated with initial length. When poststretch muscle strips were allowed to relax for 1 hand then activated by K⁺ depolarization, the developedforce remained significantly correlated with initial length. When thesame strain was applied in 23 increments to minimize peak stress,poststretch force and myosin phosphorylation increased significantly,approaching the levels expected at L_o. Furthermore,poststretch force development increased after each cycle of contractionand relaxation, approaching the control level after four cycles. Theseresults suggest that activated airway smooth muscle cells can retainrelatively precise memory of past strain when they are stretchedrapidly with high stress.

     

The Development of Fast-Start Performance in Fishes: Escape Kinematics of the Chinook Salmon (Oncorhynchus tshawytscha)

C-starts are high acceleration swimming movements critical forpredator avoidance by fishes. Since larval fishes are particularlyvulnerable to predation, C-start behavior is likely to be especiallyimportant during early life history stages. This paper examinesthe developmental changes in C-start performance with kinematicdata on immature chinook salmon (Oncorhynchus tshawytscha) (eleuthroembryostage, sensu Balon, 1975). The scaling of C-start kinematicsof immature fishes differs from that of adults. Adult C-startdurations increase with increasing body length while C-startdurations of immature fishes decrease (e.g., adult stage 1 duration[sec] = 0.0019.length [L] [cm] $ 0.026 [R² = 0.77] [Webb, 1978];eleuthroembryos stage 1 duration [sec] = –0.026L [cm]$ 0.100 [R² = 0.81]). Distance traveled during stage 2 alsodiffers between adult and immature fishes. Adult distance traveledscales directly with length (distance [cm] = 0.38L^1.01 [cm],R² = 0.96 [Webb, 1978]) while chinook eleuthroembryo distancetraveled is positively allometric with length (distance [cm]=0.37L¹³¹ [cm], R² = 0.83). There are similarities in the developmentof C-starts and burst swimming. For example, mean velocity scalessimilarly between the two locomotor modes (For burst swimming:U_mean [cm/sec] = 8.1 ± 1.1L [cm] $ 4.89 [R² = 0.86] [Webband Corolla, 1981]. For C-start stage 2: U_mean [cm/sec] = 10.96L[cm] - 14.09 [R² = 0.70]). This study demonstrates that C-startescape performance improves during early post-hatching development.Comparisons of immature chinook salmon fast-starts with dataon larval burst swimming and on adult C-starts suggest thatchanges specific to developing fish affect the scaling of kinematicparameters.     

An Analysis of Growth of Oil Palms under Nursery Conditions: II. The Effect of Spacing and Season on Growth

Three experiments on the growth of watered nursery oil palmsare described, the results of which provide estimates of seasonalvariation in net assimilation rate (E_A) and relative growth-rate(R_w) in the tropics (6° 33' N.). The range of values obtained for E_A and R_w is similar to thatfound with seedlings and during early growth in the nursery(E_A = o.I8–o.32 g/dm²/week, R_w= o.84–I.70 per cent/day)and there is very little effect of season on E_A; such variationas exists appears to be related to solar radiation. A spacing experiment indicated that E_A is independent of leafarea index (L) when L is below about 2.2, but that above thislevel E_A decreases with increasing L, falling to zero at L =5.4. The crop growth-rate (C) is maximal when L is between 2.5and 3, the maximum value observed was o.62 g/dm²/week (equivalentto 3.22 x10⁴ kg/ha/annum). These results are compared with other estimates of growth andassimilation rates of seedling, nursery and adult oil palms,and are discussed in relation to the efficiency of energy fixation,and apparent growth-rates.     

Nucleotide regulation of the voltage-dependent nonselective cation conductance in murine colonic myocytes

ATP is proposed to be a major inhibitory neurotransmitter in the gastrointestinal (GI) tract, causing hyperpolarization and smooth muscle relaxation. ATP activates small-conductance Ca²⁺-activated K⁺ channels that are involved in setting the resting membrane potential and causing inhibitory junction potentials. No reports are available examining the effects of ATP on voltage-dependent inward currents in GI smooth muscle cells. We previously reported two types of voltage-dependent inward currents in murine proximal colonic myocytes: a low-threshold voltage-activated, nonselective cation current (I_VNSCC) and a relatively high-threshold voltage-activated (L-type) Ca²⁺ current (I_L). Here we have investigated the effects of ATP on these currents. External application of ATP (1 mM) did not affect I_VNSCC or I_L in dialyzed cells. ATP (1 mM) increased I_VNSCC and decreased I_L in the perforated whole-cell configuration. UTP and UDP (1 mM) were more potent than ATP on I_VNSCC. ADP decreased I_L but had no effect on I_VNSCC. The order of effectiveness was UTP = UDP > ATP > ADP. These effects were not blocked by pyridoxal phosphate-6-azo(benzene-2,4-disulfonic acid) (PPADS), but the phospholipase C inhibitor U-73122 reversed the effects of ATP on I_VNSCC. ATP stimulation of I_VNSCC was also reversed by protein kinase C (PKC) inhibitors chelerythrine chloride or bisindolylmaleimide I. Phorbol 12,13-dibutyrate mimicked the effects of ATP. RT-PCR showed that P2Y₄ is expressed by murine colonic myocytes, and this receptor is relatively insensitive to PPADS. Our data suggest that ATP activates I_VNSCC and depresses I_L via binding of P2Y₄ receptors and stimulation of the phospholipase C/PKC pathway. inhibitory junction potentials; smooth muscle; enteric nervous system     

Are second messengers crucial for opening the pore associated with P2X7 receptor?

Stimulation of the P2X₇ receptor by ATP induces cell membrane depolarization, increase in intracellular Ca²⁺ concentration, and, in most cases, permeabilization of the cell membrane to molecules up to 900 Da. After the activation of P2X₇, at least two phenomena occur: the opening of low-conductance (8 pS) cationic channels and pore formation. At least two conflicting hypotheses have been postulated to reconcile these findings: 1) the P2X₇ pore is formed as a result of gradual permeability increase (dilation) of cationic channels, and 2) the P2X₇ pore represents a distinct channel, possibly activated by a second messenger and not directly by extracellular nucleotides. In this study, we investigated whether second messengers are necessary to open the pore associated with the P2X₇ receptor in cells that expressed the pore activity by using the patch-clamp technique in whole cell and cell-attached configurations in conjunction with fluorescent imaging. In peritoneal macrophages and 2BH4 cells, we detected permeabilization and single-channel currents in the cell-attached configuration when ATP was applied outside the membrane patch in a condition in which oxidized ATP and Lucifer yellow were maintained within the pipette. Our data support Ca²⁺ as a second messenger associated with pore formation because the permeabilization depended on the presence of intracellular Ca²⁺ and was blocked by BAPTA-AM. In addition, MAPK inhibitors (SB-203580 and PD-98059) blocked the permeabilization and single-channel currents in these cells. Together our data indicate that the P2X₇ pore depends on second messengers such as Ca²⁺ and MAP kinases. electrophysiology; pore formation     

Mechanisms of P2X7 receptor-mediated ERK1/2 phosphorylation in human astrocytoma cells

Astrocytes are involved in normal andpathological brain functions, where they become activated and undergoreactive gliosis. Astrocytes have been shown to respond toextracellular nucleotides via the activation of P2 receptors, either Gprotein-coupled P2Y receptors or P2X receptors that are ligand-gatedion channels. In this study, we have examined the manner in whichactivation of the P2X₇ nucleotide receptor, anextracellular ATP-gated ion channel expressed in astrocytes, can leadto the phosphorylation of ERK1/2. Results showed that theP2X₇ receptor agonist2',3'-O-(4-benzoyl)benzoyl-ATP induced ERK1/2phosphorylation in human astrocytoma cells overexpressing therecombinant rat P2X₇ receptor (rP2X₇-R), aresponse that was inhibited by the P2X₇ receptorantagonist, oxidized ATP. Other results suggest thatrP2X₇-R-mediated ERK1/2 phosphorylation was linked to thephosphorylation of the proline-rich/Ca²⁺-activated tyrosinekinase Pyk2, c-Src, phosphatidylinositol 3'-kinase, and proteinkinase C activities and was dependent on the presence ofextracellular Ca²⁺. These results support the hypothesisthat the P2X₇ receptor and its signaling pathways play arole in astrocyte-mediated inflammation and neurodegenerative disease.

     

Mechanosensitive tyrosine phosphorylation of paxillin and focal adhesion kinase in tracheal smooth muscle

We investigatedthe role of the integrin-associated proteins focal adhesion kinase(FAK) and paxillin as mediators of mechanosensitive signal transductionin tracheal smooth muscle. In muscle strips contracted isometricallywith ACh, we observed higher levels of tyrosine phosphorylation of FAKand paxillin at the optimal muscle length(L_o) than atshorter muscle lengths of 0.5 or 0.75 L_o. Paxillinphosphorylation was also length sensitive in muscles activated byK⁺ depolarization and adjustedrapidly to changes in muscle length imposed after contractileactivation by either ACh or K⁺depolarization. Ca²⁺ depletion didnot affect the length sensitivity of paxillin and FAK phosphorylationin muscles activated with ACh, indicating that the mechanotransductionprocess can be mediated by aCa²⁺-independent pathway. SinceCa²⁺-depleted muscles do notgenerate significant active tension, this suggests that themechanotransduction mechanism is sensitive to muscle length rather thantension. We conclude that FAK and paxillin participate in anintegrin-mediated mechanotransduction process in tracheal smoothmuscle. We propose that this pathway may initiate alterations in smoothmuscle cell structure and contractility via the remodeling of actinfilaments and/or via the mechanosensitive regulation ofsignaling molecules involved in contractile protein activation.

     

Common canonical variates

Canonical correlation analysis measures the linear relationshipbetween two random vectors X₁ and X₂ as the maximum correlationbetween linear combinations of X₁ and linear combinations ofX₂. Several generalisations of canonical correlation analysisto k2 random vectors X₁ ..., X_k have been proposed in the literature(Kettenring, 1971, 1985), based on the principle of maximisingsome generalised measure of correlation. In this paper we proposean alternative generalisation, called common canonical variates,based on the assumption that the canonical variates have thesame coefficients in all k sets of variables. This generalisationis applicable in situations where all X_i have the same dimension.We present normal theory maximum likelihood estimation of commoncanonical variates, and illustrate their use on a morphometricdata set.     

Estimating the capacity for improvement in risk prediction with a marker

Consider a set of baseline predictors X to predict a binaryoutcome D and let Y be a novel marker or predictor. This paperis concerned with evaluating the performance of the augmentedrisk model P(D = 1|Y,X) compared with the baseline model P(D= 1|X). The diagnostic likelihood ratio, DLR_X(y), quantifiesthe change in risk obtained with knowledge of Y = y for a subjectwith baseline risk factors X. The notion is commonly used inclinical medicine to quantify the increment in risk predictiondue to Y. It is contrasted here with the notion of covariate-adjustedeffect of Y in the augmented risk model. We also propose methodsfor making inference about DLR_X(y). Case–control studydesigns are accommodated. The methods provide a mechanism toinvestigate if the predictive information in Y varies with baselinecovariates. In addition, we show that when combined with a baselinerisk model and information about the population distributionof Y given X, covariate-specific predictiveness curves can beestimated. These curves are useful to an individual in decidingif ascertainment of Y is likely to be informative or not forhim. We illustrate with data from 2 studies: one is a studyof the performance of hearing screening tests for infants, andthe other concerns the value of serum creatinine in diagnosingrenal artery stenosis.