基于水稻产量构成性状间相关性的选种标准数学模型建立

选用54个水稻杂交组合F1代,对穗粒数、有效穗数、千粒重、穗谷重等产量构成性状进行相关、回归分析及其线性方程相交分析,并建立水稻选种入选标准的数学模型.结果表明:穗粒数(X_1)分别与其它三个性状间的相关达极显著水平,这四个性状的复相关系数达到极显著水平,表现为水稻产量构成性状间是互相影响、互为矛盾,构成性状间的矛盾与统一;经标准化的有效穗数(X_2)、千粒重(X_3)和穗谷重(X_4)分别依穗粒数(X_1)回归的线性回归方程分别为,x_2=0.6797-0.5907x_1,x_3=0.7268-0.4917x_1,x_4=0.2466+0.5053x_1.根据这些方程的升降性,分别组成联立方程组,求出这四个数量性状互作的矛盾统一点为:穗粒数136.6粒、有效穗数7.72穗/丛、千粒重23.53g、穗谷重3.09g;这四个性状相互作用、相互协调的优良表现型值落在穗粒数为132.3-177.0粒范围内.以穗粒数、有效穗数、千粒重、穗谷重的线性关系,建立的水稻选种入选标准数学模型具有较好的预见性和实用性.     

以比生长速率时间曲线为基础的生物群体生长数学模型

构建了一个描述限制性环境条件下生物群体生长规律的数学模型。模型中比生长速率(μ)是时间(t)的函数。模型可以很好地拟合多种生物或生物细胞群体生长的延迟期、指数期和稳定期。该模型参数少,模型参数生物学意义明确,计算简单。     

The effect of feeding on CO2 production and energy expenditure in ponies measured by indirect calorimetry and the 13C-bicarbonate technique

Energy expenditure (EE) can be estimated based on respiratory gas exchange measurements, traditionally done in respiration chambers by indirect calorimetry (IC). However, the ¹³C-bicarbonate technique (¹³C-BT) might be an alternative minimal invasive method for estimation of CO₂ production and EE in the field. In this study, four Shetland ponies were used to explore the effect of feeding on CO₂ production and EE measured simultaneously by IC and ¹³C-BT. The ponies were individually housed in respiration chambers and received either a single oral or intravenous (IV) bolus dose of ¹³C-labelled sodium bicarbonate (NaH¹³CO₃). The ponies were fed haylage 3 h before (T₋₃), simultaneously with (T₀) or 3 h after (T₊₃) administration of ¹³C-bicarbonate. The CO₂ produced and O₂ consumed by the ponies were measured for 6 h with both administration routes of ¹³C-bicarbonate at the three different feeding times. Feeding time affected the CO₂ production (P<0.001) and O₂ consumption (P<0.001), but not the respiratory quotient (RQ) measured by IC. The recovery factor (RF) of ¹³C in breath CO₂ was affected by feeding time (P<0.01) and three different RF were used in the calculation of CO₂ production measured by ¹³C-BT. An average RQ was used for the calculations of EE. There was no difference between IC and ¹³C-BT for estimation of CO₂ production. An effect of feeding time (P<0.001) on the estimated EE was found, with higher EE when feed was offered (T₀ and T₊₃) compared with when no feed was available (T₋₃) during measurements. In conclusion, this study showed that feeding time affects the RF and measurements of CO₂ production and EE. This should be considered when the ¹³C-BT is used in the field. IV administration of ¹³C-bicarbonate is recommended in future studies with horses to avoid complex ¹³C enrichment-time curves with maxima and shoulders as observed in several experiments with oral administration of ¹³C-bicarbonate.     

Evaluation of a multisensor armband in estimating energy expenditure in obese individuals

Objective: To examine the reliability and validity of the SenseWear Pro 2 Armband (SWA; Body Media, Pittsburgh, PA) during rest and exercise compared with indirect calorimetry (IC) in obese individuals. Research Methods and Procedures: Energy expenditure was assessed during rest with the SWA and IC in 142 obese adults (37 men and 105 women, BMI = 42.3 ± 7.0) and in 25 lean and overweight adults (BMI = 25.3 ± 3.2) who were used as a comparison group. Twenty‐nine of the obese adults also participated in three separate short exercise sessions including cycle ergometry, stair stepping, and treadmill walking. Results: The repeatability of SWA estimates in obese subjects was high (r = 0.88, p < 0.001). The SWA generally underestimated the resting energy expenditure (REE) (1811 ± 346 vs. 1880 ± 382 kcal/d) and highly overestimated the energy expenditure during the exercise sessions in obese individuals. REE estimations by SWA were significantly correlated with fat‐free mass (r = 0.88, p < 0.001). Bland‐Altman plots based statistical analysis for the estimated REE, and measured IC showed a low agreement (Total Error > 20% but Systematic Error < 5%) between the two methods in obese subjects, although they showed a high correlation and a very good agreement in lean and overweight patients. Discussion: The SWA is an easy to handle, practical, new portable device for measuring energy expenditure. The accuracy of the SWA appeared to be poor in the obese subjects we examined, especially those with high REE both in rest and exercise. We believe that it is necessary to incorporate new, obesity‐specific algorithms in the relative software.     

Partitioning of late gestation energy expenditure in ewes using indirect calorimetry and a linear regression approach

Abstract

Late gestation energy expenditure (EE_gest) originates from energy expenditure (EE) of development of conceptus (EE_conceptus) and EE of homeorhetic adaptation of metabolism (EE_homeorhetic). Even though EE_gest is relatively easy to quantify, its partitioning is problematic. In the present study metabolizable energy (ME) intake ranges for twin-bearing ewes were 220 – 440, 350 – 700, 350 – 900 kJ per metabolic body weight (W^0.75) at week seven, five, two pre-partum respectively. Indirect calorimetry and a linear regression approach were used to quantify EE_gest and then partition to EE_conceptus and EE_homeorhetic. Energy expenditure of basal metabolism of the non-gravid tissues (EE_bmng), derived from the intercept of the linear regression equation of retained energy [kJ/W^0.75] and ME intake [kJ/W^0.75], was 298 [kJ/W^0.75]. Values of the intercepts of the regression equations at week seven, five, and two pre-partum were 311, 398, and 451 [kJ/W^0.75], respectively. The difference between the intercepts for different weeks was used to calculate EE_homeorhetic. The remaining part of EE_gest was considered to be EE_conceptus. In conclusion, the good agreement between our values of EE_conceptus and those in the literature indicates the method's validity.     

Triaxial accelerometry for assessment of physical activity in young children

Objective: The purpose of the present study was to derive linear and non‐linear regression equations that estimate energy expenditure (EE) from triaxial accelerometer counts that can be used to quantitate activity in young children. We are unaware of any data regarding the validity of triaxial accelerometry for assessment of physical activity intensity in this age group. Research Methods and Procedures: EE for 27 girls and boys (6.0 ± 0.3 years) was assessed for nine activities (lying down, watching a video while sitting and standing, line drawing for coloring‐in, playing blocks, walking, stair climbing, ball toss, and running) using indirect calorimetry and was then estimated using a triaxial accelerometer (ActivTracer, GMS). Results: Significant correlations were observed between synthetic (synthesized tri‐axes as the vector), vertical, and horizontal accelerometer counts and EE for all activities (0.878 to 0.932 for EE). However, linear and non‐linear regression equations underestimated EE by >30% for stair climbing (up and down) and performing a ball toss. Therefore, linear and non‐linear regression equations were calculated for all activities except these two activities, and then evaluated for all activities. Linear and non‐linear regression equations using combined vertical and horizontal acceleration counts, synthetic counts, and horizontal counts demonstrated a better relationship between accelerometer counts and EE than did regression equations using vertical acceleration counts. Adjustment of the predicted value by the regression equations using the vertical/horizontal counts ratio improved the overestimation of EE for performing a ball toss. Discussion: The results suggest that triaxial accelerometry is a good tool for assessing daily EE in young children.     

Effect of feeding time on postprandial nitrogen excretion and energy expenditure in rainbow trout

The effect of feeding time (dawn or midnight) on nitrogen excretion and energy expenditure was studied in immature rainbow trout using measurements of respiratory gas exchange. Fish (mean individual weight 70 g) were maintained indoors under natural photoperiod and fed by hand (commercial food pellets) at a rate of 1% weight/day⁻¹. Rates of ammonia and CO₂ excretion and O₂ uptake were measured every hour. Ammonia excretion increased immediately after feeding in fish fed at midnight, and 2h after feeding in fish fed at dawn. Ammonia excretion and energy supply from protein catabolism, were higher in trout fed at midnight than in those fed at dawn, while total energy expenditure was the same in both groups. The results suggested that trout fed in phase with their natural feeding rhythm use dietary protein more efficiently for growth than do trout fed out of phase with the natural rhythm.     

A Weight Reduction Program Preserves Fat‐Free Mass but Not Metabolic Rate in Obese Adolescents

Objective: To determine the effects of a multidisciplinary weight reduction program on body composition and energy expenditure (EE) in severely obese adolescents. Research Methods and Procedures: Twenty‐six severely obese adolescents, 12 to 16 years old [mean BMI: 33.9 kg/m²; 41.5% fat mass (FM)] followed a 9‐month weight reduction program including moderate energy restriction and progressive endurance and resistance training. Body composition was assessed by DXA, basal metabolic rate by indirect calorimetry, and EE by whole‐body indirect calorimetry with the same activity program over 36‐hour periods before starting and 9 months after the weight reduction period. Results: Adolescents gained (least‐square mean ± SE) 2.9 ± 0.2 cm in height, lost 16.9 ± 1.3 kg body weight (BW), 15.2 ± 0.9 kg FM, and 1.8 ± 0.5 kg fat‐free mass (FFM) (p < 0.001). Basal metabolic rate, sleeping, sedentary, and daily EE were 8% to 14% lower 9 months after starting (p < 0.001) and still 6% to 12% lower after adjustment for FFM (p < 0.05). Energy cost of walking decreased by 22% (p < 0.001). The reduction in heart rate during sleep and sedentary activities (?10 to ?13 beats/min), and walking (?20 to ?25 beats/min) (p < 0.001) resulted from both the decrease in BW and physical training. Discussion: A weight reduction program combining moderate energy restriction and physical training in severely obese adolescents resulted in great BW and FM losses and improvement of cardiovascular fitness but did not prevent the decline in EE even after adjustment for FFM.     

MedGem hand-held indirect calorimeter is valid for resting energy expenditure measurement in healthy children

Objective: To assess the validity of a new hand‐held indirect calorimeter [MedGem (MG)] in the determination of resting energy expenditure (REE; kilocalories per day) in children. Research Methods and Procedures: One hundred male (n = 54) and female (n = 46) children (10.6 ± 3.2 years, 43.9 ± 19.0 kg, 146.1 ± 18.8 cm, 19.6 ± 4.9 kg/m²) participated. Children arrived at the University of Oklahoma body composition laboratory between 5:30 am and 6:15 am after an overnight fast. On arrival, subjects voided and remained quietly in the supine position for 15 minutes before testing. REE was measured by indirect calorimetry (in random order), with both the MG (sitting upright) and the criterion Delta Trac II (DT) (supine). Data are reported as the mean ± standard deviation. Results: The mean MG REE (1452 ± 355 kcal/d) was significantly higher than DT REE (1349 ± 296 kcal/d, p < 0.001). Bland‐Altman analysis revealed a mean bias (MG ? DT) of 104 kcal/d, with limits of agreement of ?241 to +449 kcal/d. To examine the difference in subject positioning, an independent sample of 38 subjects performed the MG in its normal position (sitting) and holding the MG in a supine position. REE by the MG in the sitting position (1475 ± 350 kcal/d) was significantly (p < 0.05) higher than the MG in the supine position (1419 ± 286 kcal/d). Discussion: The mean difference in REE between MG and DT was relatively small (103 kcal/d) but significant; however, a portion of this difference may have been related to differences in subject positioning. These preliminary data indicate that the MG shows promise as a valid tool in the assessment of REE in children.     

Quantification of the energy expenditure during training exercises in Standardbred trotters

An appropriate energy feeding management that ensures the optimal dietary energy supply according to the energy expenditure (EE) is a crucial component for the horse’s performance. The main purpose of this study was to determine the EE during four specific exercises used in the training of Standardbred trotters (promenade, jogging, parcours and interval work-outs). A total of six Standardbred geldings performed four different testing situations on a track. The intensity (expressed in percentage of the maximal velocity over 500 m, i.e. v500) and volume (distance and duration) of the testing situations were determined according to practices reported by French trainers. Promenade and jogging included only an exercise phase, whereas parcours and interval situations also included a warm-up and a recovery phase. Oxygen uptake (VO₂), carbon dioxide production (VCO₂) and heart rate (HR) were continuously recorded from 2 min before the beginning through to the end of the testing situations, using a portable respiratory gas analyser. Blood lactate levels and rectal temperature were determined before and immediately after the exercise phase of each testing situations. EE of the different phases (warm-up, exercise and recovery) and EE of the entire testing situations (EE_TOTAL) were calculated from VO₂ measurements and the O₂ caloric equivalent. Interval and parcours situations induced higher physiological responses than promenade and jogging situations, particularly in terms of VO_2peak, VCO_2peak and HR_peak. The highest blood lactate concentration (6 mmol/l) was measured after the interval exercise, and respiratory exchange ratios ⩾1 were observed only for the parcours situation. The EE of exercise phase varied from 0.49 to 1.79 kJ/min per kg for promenade and parcours situations. The EE of warm-up and recovery phases did not differ between parcours and interval situations, and was estimated at 1.04 and 0.57 kJ/min per kg BW, respectively. On average, the warm-up and the recovery phases contributed to 38% and 19% of the EE_TOTAL. For promenade, jogging, parcours and interval situations, EE_TOTAL was evaluated at 12 618, 11 119, 13 698 and 18 119 kJ, respectively.     

A mathematical model for the leukocyte filtration process

Leukocyte filters are applied clinically to remove leukocytes from blood. In order to optimize leukocyte filters, a mathematical model to describe the leukocyte filtration process was developed by modification of a general theoretical model for depth filtration. The model presented here can be used to predict the time-dependent leukocyte filtration as a function of cell-cell interaction in the filter, filter efficiency, filter capacity, filter dimensions, and leukocyte concentration in the suspension applied to the filter. The results of different leukocyte filtration experiments previously reported in the literature could be well described by the present model. (c) 1995 John Wiley & Sons, Inc.