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PubMed1992

Right ventricular preload recruitable stroke work, end-systolic pressure-volume, and dP/dtmax-end-diastolic volume relations compared as indexes of right ventricular contractile performance in conscious dogs.

Three indexes developed originally to assess left ventricular contractile performance were applied instead to the right ventricle (RV) in 11 conscious dogs: the relation between stroke work and end-diastolic volume (EDV), termed the preload recruitable stroke work (PRSW) relation; the end-systolic pressure-volume (ESPV) relation; and the maximum dP/dt (dP/dtmax)-EDV relation. The reproducibility, inotropic sensitivity, chronotropic sensitivity, and afterload sensitivity of these RV relations were compared. RV volume was determined with an ellipsoidal shell subtraction model from orthogonal dimensions measured by sonomicrometry. RV transmural pressure was measured with micromanometers. After autonomic blockade, preload was varied by repeated, transient vena caval occlusions before and during partial occlusion of the main pulmonary artery, after release of the pulmonary arterial occlusion, after calcium infusion, and over a range of heart rates induced by atrial pacing. The slope and volume-axis intercept of the PRSW relation were more reproducible (SD/mean, 7.8 +/- 3.3% and 6.2 +/- 4.1%, respectively) than the slope and volume-axis intercept of the ESPV relation (10.1 +/- 6.7% and 23.0 +/- 31.3%, both p less than 0.05) or the slope and volume-axis intercept of the dP/dtmax-EDV relation (43.4 +/- 70.4% and 153.8 +/- 184.6%, both p less than 0.05). The slope of the PRSW relation increased 32 +/- 17% (p less than 0.05) after calcium infusion, but the volume-axis intercept did not change significantly. In contrast, the slopes of the ESPV and dP/dtmax-EDV relations did not change significantly after calcium infusion, but the volume-axis intercepts decreased significantly (both p less than 0.05). Despite a 71 +/- 26% increase in mean RV ejection pressure during partial occlusion of the main pulmonary artery, the slopes and volume-axis intercepts of both the PRSW and dP/dtmax-EDV relations did not change significantly, but the slope of the ESPV relation increased 45 +/- 22% (p less than 0.05) without significant change in the volume-axis intercept. None of the relations demonstrated significant chronotropic sensitivity. The PRSW relation is the preferred index of RV contractile performance because 1) it is the most reproducible, 2) its slope alone sensitively detects changes in contractile state, and 3) unlike the ESPV relation, it is relatively insensitive to afterload.

Animals↗
PubMed1989

Comparison between a 30-s all-out test and a time-work test on a cycle ergometer.

The relationship between the amount of work (Wlim) performed at the end of constant-power exhausting exercise and exhaustion time (tlim) has been studied for supramaximal exercise [105%, 120%, 135% and 150% of the individual maximal aerobic power, (MAP)] performed on a Monark cycle ergometer in nine men. The Wlim--tlim relationship was described by a linear relationship (Wlim = a + b . tlim). Intercept a was roughly equivalent to the work produced during a 1-min exercise performed at MAP. Slope b was equal to 79% of MAP. Intercept a has been correlated with the total amount of work (AW) performed during a 30-s all-out test supposed to assess anaerobic capacity. Intercept a was significantly (p less than 0.05) correlated with AW. The anaerobic capacity was not depleted at the end of the all-out test, as the mechanical power at the 30th s of this test was approximately equal to twice MAP. However, AW was significantly higher than intercept a. It was likely that the value of intercept a was an underestimation of the maximal anaerobic capacity because of the inertia of the aerobic metabolism. Indeed, an exponential model of the Wlim--tlim relationship, which takes the interia of the aerobic metabolism into account, shows that a linear approximation of the Wlim--tlim relationship yields a systematic underestimation of the anaerobic capacity. Consequently, intercept a of the Wlim--tlim relationship is not a more accurate estimation of the anaerobic capacity than the AW performed during a 30-s all-out test.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Pulse oximetry fails to accurately detect low levels of arterial hemoglobin oxygen saturation in dogs.

The accuracy of two commercially available pulse oximeters (the Ohmeda Biox 3700, software version "J," and the Nellcor N-100) in detecting low levels of arterial hemoglobin oxygen saturation (SaO2) was evaluated in 10 dogs in which hypoxia was induced by stopping the fresh gas flow into the anesthesia machine circle system. Measurements made in vivo with the pulse oximeters, with detectors placed on the tongue, were compared with measurements made in vitro using an IL 282 CO-Oximeter as SaO2 decreased toward zero. Measurements from the two oximeters correlated poorly over the range from 0 to 100% SaO2 (r = 0.69). In this range, the correlation between Nellcor N-100 measurements and those of the CO-Oximeter had an r of 0.82, a regression line slope of 0.82, and a y intercept of 14.8; the correlation between the Ohmeda Biox 3700 and the CO-Oximeter had an r of 0.83, a regression line slope of 0.66, and a y intercept of 32.7. The correlation with the CO-Oximeter was similar for both the Ohmeda and the Nellcor pulse oximeters at an SaO2 of 80% or more. However, when SaO2 was less than 80%, measurements by pulse oximetry correlated less well with CO-Oximeter measurements (r = 0.62, slope = 0.64, and y intercept = 21.0 for Nellcor; r = 0.71, slope = 0.67, and y intercept = 32.4 for Ohmeda). When SaO2 was less than 60%, both oximeters inaccurately indicated the co-oximetry values (r = 0.36 and y intercept = 26.1 for the Nellcor; r = 0.48 and y intercept = 33.2 for the Ohmeda).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2004

Emetine ditartrate: a possible lead for emergency contraception.

Interception of pregnancy in its initial stage is an attractive and viable approach to contraception. A chemical agent, taken within the first few days of missed menses, intercepts the conception, which is expelled with menstrual flow. The main targets of such agents are the uterus, blastocyst and the growing trophoblasts, whose nutritional requirement is inhibited. Our previous work has identified several nonsteroidal chemical entities as pregnancy interceptives in rodents and infrahuman primates. However, none reached clinical stage due to their ineffectiveness by oral route. Nevertheless, parallel to these rationally designed synthetic compounds, a program was ongoing to identify natural product(s) that can be used as interceptives. We are reporting for the first time the detailed profile of emetine ditartrate, a compound whose pregnancy interceptive efficacy has been studied in mouse, rat, hamster, guinea pig and rabbit by oral and intravaginal routes of administration. By the oral route, the compound caused 100% resorption of the fetuses in rat, hamster and guinea pig at 6.0, 5.0 and 3.0 mg/kg, respectively, on administration during peri- and early postimplantation periods of pregnancy (depending upon the day of implantation in each species). By intravaginal route, the compound was administered once in the form of a vaginal pessary on the day of implantation in respective species; interception of pregnancy was not achieved completely in rat and hamster at doses four to five times the oral dose in multi-day schedule. However, in guinea pig and rabbit it was fully effective at 7.0 and 70.0 mg/animal, respectively. The compound was devoid of estrogenic, antiestrogenic and progestational activity but possessed mild antiprogestational activity at the high dose in vivo. In in vitro assay, however, it did not show any significant binding to estrogen and progesterone receptors. The mode of action of the compound was found to be mainly on the uterus and early embryos around implantation, possibly on the trophoblasts and endometrial cells at the attachment site. The absence of 100% efficacy in rat and hamster by intravaginal route, but not by oral route, is possibly due to poor absorption of the compound through the vagina in these species. The guinea pig and rabbit, therefore, seem the better species for evaluating the efficacy of the compound administered by the vaginal route.

Administration, Intravaginal↗
PubMed1995

Sensitive and specific determination of the equivalence of absorption rates.

PURPOSE: To develop a new method for the direct, sensitive evaluation of the equivalence of absorption rates in linear kinetic systems. METHODS: Concentrations are obtained before the earlier peak. Ratios of concentrations adjusted for the corresponding ratio of AUCs (area under the curve contrasting plasma concentration with time), or their logarithm, are extrapolated by linear regression to the time of drug administration. The intercept estimates the ratio of absorption rate constants (ka), or its logarithm. RESULTS: The intercept metric assesses the equivalence of absorption rates with very favourable characteristics. The metric reflects the ka-ratio specifically (i.e., not affected by other kinetic parameters), is approximately linear to it, exhibits high kinetic sensitivity and excellent statistical properties. With many observations, the intercept metric has near-ideal features, including high power for determining bioequivalence and the ability to detect a 25% difference between ka values. With only 3 or 4 measurements before the earlier peak, the performance of the metric depends on the preset regulatory conditions. Reasonably good power is noted if the bioequivalence limits determine a 50% difference between two metrics and, approximately, between two ka values. The intercept metric shows very high power with a wider bioequivalence range. The power declines only moderately with increasing intraindividual variation of ka. The equivalence of absorption rates is assessed with much higher power by the intercept metric than by Cmax. CONCLUSIONS: The excellent kinetic and statistical properties of the intercept metric enable the specific and sensitive determination of the equivalence of absorption rates.

Absorption↗
PubMed1995

Hormonal anti-implantation agents: antiprogestins.

Oestrogens and progestogens separately or in combination are able to prevent implantation with high efficiency, thus acting as interceptive agents. Current interceptive medical regimens include high-dose oestrogens, the association of oestrogens with progestogens or progestogens alone. Compounds with antiprogesterone properties, such as RU 486 (mifepristone) or ZK 98734 (lilopristone), also exhibit a strong interceptive action which, as shown in animal models, is proportional to the dose and the day(s) of administration. Recent clinical studies show that RU 486 can be used successfully for postcoital interception. The regimen applied for this purpose consists of the intake of a single dose of 600 mg RU 486 within 72 h of a single act of unprotected intercourse. This treatment was found to be highly effective and to have a more favourably side-effect profile in comparison with the oestrogen-progestogen interceptive regimen. However, because of the induced irregularities of the cycle, the mifepristone regimen, as with the other hormonal methods, should not be used on a regular basis. Currently, all interceptive hormonal regimens are emergency methods. Their occasional use to prevent unwanted pregnancies may reduce the number of therapeutic abortions. However, the frequency and extent of their side-effects do not allow for a repeated postcoital use after every act of unprotected intercourse. Obviously, the development of an effective and safe 'morning after pill' requires further basic and clinical investigations.

Animals↗
PubMed2002

The relationship of heart rate reserve to VO2 reserve in patients with heart disease.

UNLABELLED: Recent reports indicate that among healthy adults, % heart rate reserve (HRR) is more closely related to %VO2 reserve (VO2R) than it is to %VO2max. This finding, in addition to the disparity between %HRR and %VO2max which is greater at low intensities and among low fit individuals, led the American College of Sports Medicine to adopt the use of %VO2R in place of %VO2max when prescribing exercise intensity among healthy adults and persons with heart disease. However, the relationship of %HRR to %VO2R among persons with heart disease has not been described. PURPOSE: Among patients with a myocardial infarction (MI) and patients with chronic heart failure (HF), test the hypothesis that %VO2R is equivalent to %HRR, while %VO2peak is not. METHODS: Using a clinical cardiology outcomes database, symptom-limited treadmill tests from 65 patients with MI and 72 patients with HF were identified. Heart rate and VO2 data were measured continuously and averaged every 15 s. For each subject, linear regression was used to calculate the slope and y-intercept of %HRR versus %VO2R (assuming rest VO2 = 3.5 mL x kg(-1) x min(-1)) and %HRR versus %VO2peak. Mean slope and y-intercept were calculated for each group and compared with the line of identity (slope = 1, y-intercept = 0). RESULTS: For the MI and HF groups, the slope of %HRR versus %VO2R was 0.96 +/- 0.02 (+/-SE; P = NS, slope vs 1) and 0.97 +/- 0.02 (P = NS), respectively. And the y-intercept was -1.9 +/- 2.1% (P = NS, y-intercept vs 0) and -5.9 +/- 2.1% (P < 0.05) for MI and HF, respectively. For both patient groups, the regression of %HRR versus %VO2peak resulted in a line that differed (P < 0.001) in both slope and y-intercept from the line of identity. CONCLUSIONS: In patients with heart disease, %HRR is a better estimate of %VO2R than %VO2peak. This finding does not affect the current recommended use of %HRR. However, when prescribing exercise based on VO2, relative intensity should be expressed as %VO2R.

Aged↗
PubMed2003

Morphological quantification of emphysema in small human lung specimens: comparison of methods and relation with clinical data.

Small human lung specimens are frequently used for cell biological studies of the pathogenesis of emphysema. In general, lung function and other clinical parameters are used to establish the presence and severity of emphysema/chronic obstructive pulmonary disease without morphological analysis of the specimens under investigation. In this study we compared three morphological methods to analyze emphysema, and evaluated whether clinical data correlate with the morphological data of individual lung samples. A total of 306 lung specimens from resected lung(lobes) from 221 patients were inflated and characterized using three morphological parameters: the Destructive Index, the Mean Linear Intercept, and Section Assessment. Morphological data were related to each other, to lung function data, and to smoking behavior. Significant correlations (P < .001) were observed between Section Assessment and Destructive Index (r = 0.92), Mean Linear Intercept with Destructive Index (r = 0.69) and Mean Linear Intercept with Section Assessment (r = 0.65). Section Assessment, being much less time consuming than Mean Linear Intercept and Destructive Index, is the parameter of choice for initial analysis. Destructive Index is the most sensitive parameter. There was a significant (P < .001), but weak correlation for all three parameters with the diffusion capacity for CO (K(CO)) (Destructive Index: r = -0.28; Mean Linear Intercept: r = -0.34; Section Assessment: r = -0.32), and with FEV(1)/IVC (Destructive Index: r = -0.29; Mean Linear Intercept: r = -0.33; Section Assessment: r = -0.28), but not with other lung function parameters. A significant difference (P < .05) between (ex-) smokers and never-smokers was observed for Destructive Index and Section Assessment. It is concluded that the application of the three morphological parameters represents a useful method to characterize emphysematous lesions in a (semi-)quantitative manner in small human lung specimens, and that Section Assessment is a suitable and fast method for initial screening. The extent of emphysema of individual lung specimens should be established by means of morphometry, rather than lung function data.

Adult↗
PubMed1988

Changes in coronary pressure-flow relation after transition from blood to Tyrode perfusion.

In six isolated, diastolic-arrested, maximally vasodilated cat hearts, we studied changes in coronary pressure-flow relations (zero-flow pressure intercept, resistance) during the first 25 min, after a change of perfusate, from blood to Tyrode. The apparent intercept (zero-flow) pressure changed from 2.0 +/- 0.94 (+/- SD) kPa during blood perfusion to 2.5 +/- 0.55, 2.6 +/- 0.68, 2.5 +/- 0.94, and 2.7 +/- 1.34 kPa during Tyrode perfusion for 2:15, 5:30, 10:30, and 25:00 min, respectively. Intercept pressures during Tyrode perfusion were significantly different from the intercept pressure during blood perfusion, except for the one measured after 25 min of Tyrode perfusion (P less than 0.05). Resistance (defined as the ratio of perfusion pressure and flow at 10 kPa perfusion pressure) steadily rose to approximately 170% of the value during blood perfusion. The observation that the apparent intercept pressure is maintained, when a particle-free (Newtonian) isotonic perfusate is used, may indicate that this intercept is not a result of blood rheology alone. The increase rather than decrease in resistance suggests an effect of edema, which increases interstitial volume at the expense of intravascular volume.

Animals↗
PubMed1986

Precision of measurements of right and left ventricular volume by cine computed tomography.

Precise determination of left and right ventricular stroke volumes is limited with conventional imaging techniques. We determined whether right and left ventricular stroke volumes could be precisely measured with cine computed tomography (CT). Cine CT enables simultaneous imaging of the right and left ventricles at an 8 mm slice thickness with a maximal scanning rate of 17 frames/sec (50 msec acquisition intervals). In eight dogs, true right ventricular and left ventricular stroke volumes were determined by dividing thermodilution cardiac output by heart rate and/or with the use of an aortic electromagnetic flow probe implanted over a long term. After at least 5 sec of suspended respiration, cine CT images were acquired during central venous injection of a nonionic contrast agent. Multiple perturbations in stroke volume were induced in each dog by the administration of dobutamine, sodium pentobarbital, or sodium nitroprusside or by coronary artery occlusion. Right and left ventricular stroke volumes were obtained by Simpson's reconstruction of end-diastolic and end-systolic short-axis tomograms from apex to base. The cine CT left ventricular stroke volume (range 11 to 45 ml) correlated highly with the true left ventricular stroke volume (r = .99, slope = 1.01, y intercept = -0.2 ml, SEE = 1.5 ml, n = 25). The cine CT right ventricular stroke volume (range 11 to 34 ml) also correlated highly with the true right ventricular stroke volume (r = .98, slope = 0.9, y intercept = 2.2 ml, SEE = 1.7 ml, n = 15). In 12 studies, the mean difference between nearly simultaneous right and left ventricular stroke volumes by cine CT was 1.1 ml (range 0.1 to 3.2 ml). Calculation of right and left ventricular stroke volumes from data from cine CT were highly reproducible. Intraobserver variability in measurements of right ventricular stroke volume (r = 1.0, slope = 0.99, y intercept = 0.19 ml) and left ventricular stroke volume (r = 1.0, slope = 1.02, y intercept = -0.21 ml) was minimal. Interobserver variability in measurements of right ventricular stroke volume (r = .98, slope = 0.90, y intercept = 1.66 ml) and left ventricular stroke volume (r = .99, slope = 0.97, y intercept = -0.02 ml) was likewise minimal. Thus, precise and highly reproducible measurements of right and left ventricular stroke volumes can be obtained with cine CT.

Animals↗
PubMed1993

The influence of high-intensity exercise training on the Wlim-Tlim relationship.

When exercise to exhaustion is performed using at least two different intensities, work to fatigue (Wlim) can be expressed as a linear function of time to fatigue (Tlim). Whereas the slope of this function is related to endurance ability, the y-intercept is associated with the potential to perform high intensity interval exercise. The purpose of the present investigation was to determine the influence of 8-wk intermittent high-intensity exercise training on the y-intercept derived from the Wlim-Tlim relationship. Eight healthy, untrained male students (19.1 +/- 0.6 yr) completed five 60-s bouts of maximal exercise on the cycle ergometer, three times a week, for 8 wk. Seven controls avoided regular activity for the same period. Prior to and immediately following the training period, the Wlim-Tlim relationship, VO2max, and total work completed in five 60-s exercise bouts on the cycle ergometer were determined. Correlational analysis established relationships between the y-intercept and total work accomplished in the interval test pre- (r = 0.90; P < 0.01; N = 15) and post-training (r = 0.92; P < 0.01; N = 15), confirming that the y-intercept is related to the ability to perform exercise of this nature. Moreover, the "anaerobic" energy yield, calculated from total work and oxygen consumed during the interval exercise, was also related to the y-intercept (r = 0.78; P < 0.01). Interval training significantly increased both the y-intercept (P = 0.0015) and total work accomplished in the interval test (P = 0.001), while the slope of the Wlim-Tlim relationship (critical power) remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1995

Issues relating to normalization of body fat content in men and women.

OBJECTIVE: Body mass index (BMI), % body fat, and the fat:lean ratio are ratios frequently used as obesity indices. Ratios are based on an assumption that the regression between the numerator (e.g. fat mass) and the denominator (e.g. body mass) has a zero-intercept. As shown in the companion paper, non-zero intercepts cause several problems when ratios are used to adjust data and analysis of covariance (ANCOVA) is frequently the preferred statistical tool. The purpose of this paper is to examine whether BMI, % body fat and the fat:lean ratio meet the necessary criteria for suitable obesity indices using gender comparisons as an example. RESULTS: In 720 healthy men and women, BMI was higher in men (24.9 +/- 3.3 vs 23.4 +/- 3.2 kg/m2, P < 0.001), but fat mass, % fat and the fat:lean ratio were higher in women (14.8 +/- 8.4 vs 19.1 +/- 8.1 kg fat; 18.6 +/- 8.7 vs 29.9 +/- 9.7% body fat; 0.24 +/- 0.14 vs 0.46 +/- 0.20 for the fat:lean ratio; P < 0.001). Body mass (BM) was correlated with height2 in men (r = 0.40) and women (r = 0.36) with equivalent regression slopes (17.1 +/- 1.9 vs 15.6 +/- 2.3 kg per m2 in women), but the intercepts were different from zero (24.1 kg in men, 20.7 kg in women). When BM was adjusted for height2 using ANCOVA, men remained significantly heavier than women (74.4 +/- 11.0 vs 68.8 +/- 11.6 kg; P < 0.001). Fat mass (FM) was significantly correlated with BM in males (r = 0.64) and females (r = 0.78) but the regression slopes were different (0.49 +/- 0.03 vs 0.71 +/- 0.03 kg of fat per kg body mass in females; P < 0.05) and the intercepts were different from zero (-23.2 +/- 2.2 kg in males; -24.8 +/- 2.1 kg in females). FM adjusted for BM was significantly higher in women (11.7 vs 25.6 kg). FM was inversely correlated with fat free mass (FFM) in males (r = -0.17) and females (r = -0.20), with similar regression slopes (-0.16 +/- 0.05 vs -0.26 +/- 0.08 kg of FM per kg of FFM in women) and the intercepts were significantly different from zero (24.8 +/- 3.0 kg in males; 30.7 +/- 3.6 kg in females). When FM was adjusted for FFM, there was no significant difference between men (16.3 kg) and women (17.0 kg). CONCLUSIONS: It is concluded that: (a) the presence of significant intercepts does not support the use of ratios as obesity indices and regression based models should be considered; and, (b) the direction and magnitude of the difference in obesity index between men and women changes with different normalization approaches.

Adolescent↗
PubMed1996

The influence of resistance training on the critical power function & time to fatigue at critical power.

The present study examined whether a six-week resistance training program would influence the critical power (CP) function, time to exhaustion (TE) at CP and/or peak oxygen uptake (VO2 peak). The CP function is believed to provide an index of endurance ability (CP given by the slope), and anaerobic work capacity (the y-intercept). Eight healthy, untrained males undertook lower-body resistance training (90 min/day, 3-4 times/wk) for six weeks; eight controls refrained from resistance or endurance training for the same period. Before and immediately following the training period, subjects completed three trials to determine their CP function, a test of VO2 peak, a one-repetition maximum (1-RM) leg press test and TE at their CP. Training significantly increased both 1-RM leg press (28.6%, P < 0.05) and the y-intercept (34.9%, P < 0.05) while no changes in CP, VO2 peak or TE (p > 0.05) were found. Changes in the y-intercept following resistance training were negatively correlated with changes in the CP (r = -0.94, p < 0.05, N = 8). The present data show that the y-intercept of the CP function is sensitive to, and modified by, six weeks of resistance training. Given that resistance training had no significant influence on CP, TE at CP or VO2 peak, the present study has also shown that six weeks of resistance training will not alter indices of endurance ability. The negative relationship between changes in the y-intercept and CP exposes a potential limitation of the linear CP function when evaluating changes in endurance ability following an intervention which significantly alters the y-intercept.

Adolescent↗
PubMed2000

Critical power of knee extension exercises does not depend upon maximal strength.

A possible dependence of critical power (CP) and the Y-intercept of the work/exhaustion time relationship (Y(intercept)) on maximal muscular strength of the same muscle group has been studied in nine endurance-trained subjects, seven gymnasts, and seven weight-lifters. CP was calculated as being equal to the slope of the linear relationship between exhaustion time and the work performed at exhaustion on a knee extension ergometer. Y(intercept) was equal to the intercept between this relationship and the work axis. The muscular strength of the knee was evaluated by measuring the torques exerted on a Biodex knee isokinetic dynamometer at four angular velocities: 0 degrees x s(-1) (T0), 90 degrees x s(-1) (T90), 180 degrees x s(-1) (T180) and 240 degrees x s(-1) (T240). The results of the present study do not support the hypothesis that CP depends upon maximal strength. Indeed, CP was not correlated with T0, T90, T180 or T240 (¿r¿ < 0.01). Y(intercept) was significantly and positively correlated only with T90.

Adult↗
PubMed1989

Normal postmenopausal women show iliac crest trabecular thickening on vertical sections.

Trabecular thickness and the trabecular star volume were estimated in 49 normal individuals (20 males and 29 females) using an unbiased sampling procedure consisting of anisotropic, vertical sections, and a corresponding anisotropic test system. Eight-microns-thick undecalcified stained vertical sections were obtained from iliac crest specimens. Implying a trabecular plate model mean trabecular thickness (Tb.Th., microns) was estimated by different methods: (a) the ratio between bone volume and bone surface (Tb.Th.ratio); (b) the mean of the orthogonal intercepts multiplied with pi/4 (Tb.Th.l0); and (c) the mean of random linear intercepts divided by 2 (Tb.Th.l1). Trabecular star volume (Vtr*, mm3), a true three-dimensional size parameter independent on any model, was estimated using linear intercepts in random directions. Significant (2p less than 0.001) correlations were found between the different methods with coefficients of correlation ranging from 0.71 to 0.89. The Tb.Th. ratio was overall higher (155 +/- 31 microns, (X, SD), 2p less than 0.001) than the other linear estimates, Tb.Th.l0: 144 +/- 26 microns and Tb.Th.l1: 135 +/- 27 microns. Estimates based on orthogonal intercepts (l0) were slightly higher (2p less than 0.001) than those from random linear intercepts (l1). Among all the individuals no significant age-related changes were seen in the measured parameters. However, postmenopausal women (greater than 50 years of age) had more thick trabeculae than younger women (2p = 0.03). Intra-individual distribution analysis disclosed that this finding could not be explained by preferential perforation and loss of thinner trabeculae during bone remodeling. Therefore, normal postmenopausal women do increase trabecular thickness with age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2003

Catching oriented objects.

We have investigated how participants match the orientation of a line, which moves on a vertical screen towards the subject. On its path to the participant, the line could disappear at several positions. Participants were instructed to put a bar on a predefined interception point on the screen, such that the bar touched the screen with the same orientation as the moving line at the very moment when the line passed through the interception point or (in case of line disappearance) when the hidden line would pass through the interception point (like in catching). Participants made significant errors for oblique orientations, but not for vertical and horizontal orientations of the moving line. These errors were small or absent when the moving line was visible all the way along its path on the screen. However, these errors became larger when the line disappeared farther away from the interception point. In the second experiment we tested whether these errors could be related to errors in visual perception of line orientation. The results demonstrate that errors in matching of the bar do not correspond to the last perceived orientation of the line, but rather to the perceived orientation of the moving line near the beginning of the movement path. This corresponds to earlier observations that participants shortly track a moving target and then make a saccadic eye movement to the interception point.

Hand Strength↗
PubMed2003

Longitudinal serological responses to Salmonella enterica of growing pigs in a subclinically infected herd.

A longitudinal survey was conducted in France in a subclinically Salmonella-infected farrow-to-finish pig farm to describe the time-course of the serological response to Salmonella enterica in growing pigs. We used three batches of sows and their corresponding litters (n = 31 litters). Among these, 256 pigs randomly selected and individually identified were followed from the first week of age until slaughter. Serial individual blood samples were submitted to indirect Salmonella-ELISA testing. Salmonella shedding was investigated by bacteriological testing of faecal material regularly collected from the sows and pigs and by environment swabs taken from the pens. Caecal contamination was checked at the slaughterhouse. Information about litter composition (filiation), location of the pigs in post-weaning and fattening pens, sanitary events, sex and body weights was recorded. 11.6% of the pigs shed S. enterica; 52% of pigs seroconverted before slaughter. The age-related variation of the natural logarithm of calibrated optical densities (COD) of pigs was described with two linear mixed models. From 8 to 61 days of age, the decrease in COD with age was fitted with a model including random effects of the animal and the dam on the intercept and slope, a batch random effect on the intercept and an individual birth-weight fixed effect on the intercept. The dam random effect was explained by the parity of the sow, Salmonella shedding by the sow during the farrowing phase and the value of the optical density of colostrum collected at parturition. A second model fitting the increase in COD from 61 days of age until slaughter included the random effect on intercept of the batch and the random effects on slope and intercept of the animal, the dam and the pen in which the followed animals were located during the fattening phase and the environmental contamination as fixed effect. In this second model, no relation was found between individual slaughter-bacteriological results and increasing COD values. Considering seroconversion time between 61 days of age and slaughter, survival function were constructed using the Cox proportional-hazards model. Both methods suggested that seroconversions generally occurred during the last third of the fattening phase (from 140 days of age to slaughter), while shedding was observed during the first half of the fattening period. The fitted models suggest the existence of clusters (such as pen and litter of origin).

Animal Husbandry↗
PubMed1992

Pressure-flow relationships of the pulmonary circulation during endotoxin infusion in intact dogs.

BACKGROUND AND METHODS: We aimed to characterize the effects of an endotoxin insult (Escherichia coli 0127:B8) on the relationships between pulmonary vascular pressure and flow in intact dogs. To achieve this goal, multipoint plots of total pressure gradient, arterial pressure gradient, and venous pressure gradient vs. flow were generated by graded inflation of a right atrial balloon, which was used to vary flow. The partitioning of the total pressure decrease across the pulmonary vasculature (total pressure gradient = pulmonary arterial pressure-pulmonary artery occlusion pressure [PAOP]) into gradients across pulmonary arterial (arterial pressure gradient = pulmonary arterial pressure--effective capillary pressure) and pulmonary venous (venous pressure gradient = effective capillary pressure--PAOP) regions was assessed by a waveform mathematical analysis of the pulmonary arterial pressure profile during arterial occlusion, with computation of both PAOP and effective pulmonary capillary pressures. Slopes and extrapolated pressure intercepts from linear regression fits to the pulmonary vascular pressure/flow plots were determined in seven dogs after a 2-hr endotoxic infusion interval and were compared with the corresponding values that characterized a similar group of sham-operated dogs. RESULTS: Under normal conditions, the extrapolated pressure intercept for pulmonary arterial pressure gradient was virtually 0 mm Hg; for total pulmonary arterial pressure gradient and pulmonary venous pressure gradient, the mean extrapolated pressure intercepts were substantially positive: 2.4 +/- 0.2 and 2.1 +/- 0.3 mm Hg, respectively. Endotoxin infusion at 0.25 micrograms/kg/min significantly increased the pressure intercepts from 2.4 to 8.7 and from 2.1 to 8.3 mm Hg of total pressure gradient and venous pressure gradient vs. flow, respectively. This infusion produced a minor, nonsignificant change in the intercept of arterial pressure gradient vs. flow, whereas it increased its slope significantly (p less than .05) from 0.036 to 0.081 mm Hg/mL/min/kg. CONCLUSIONS: These data suggest that endotoxin's effects on vascular resistance are exerted at two different loci such that these effects are additive. These endotoxin-induced effects consisted of increased vascular resistance of the arterial segment and appearance of a Starling resistor at the venous side of the pulmonary circulation, which acted as the relevant back-pressure to flow.

Animals↗