The role of characteristic motion in object categorization

We report three experiments where we investigated the role of movement in object recognition. Previous studies have suggested a distinct and separate mechanism for object motion encoding, related to the action or motor-based system. To date, however, the role of an object's motion in long-term memory representations has not been explicitly tested. Here we were specifically interested in whether an object's characteristic motion patterns are integrated with static properties in an object's representation in memory. To that end, we used a simple categorization task where novel objects were categorized on the basis of two static (color and shape) and two dynamic (action and path) properties. The "action" of an object referred to its intrinsic motion pattern, whereas "path" referred to an object's extrinsic motion pattern (i.e., the route an object took). In Experiment 1, we found that all properties were relevant for categorization with the exception of path. This result was not due to path being less salient than other properties (Experiment 2). In Experiment 3, we found that when the action property was redundant that path was now used for categorization, suggesting that path was not used with action in Experiment 1 because of temporal order effects. Our findings argue for a cue-integrated model of object representation in memory.     

Modelling HIV-RNA viral load in vertically infected children

Human immunodeficiency virus (HIV) ribo-nucleic acid (RNA) viral load is a measure of actively replicating virus and is used as a marker of disease progression. For a thorough understanding of the dynamics of the evolution of the virus in the early life of HIV-1 vertically infected children, it is important to elucidate the pattern of HIV-RNA viral load over age. An aspect of assay systems used in the quantification of RNA viral load is that they measure values above particular cut-off values for detection, below which the assays used are not sufficiently sensitive. In this way, measurements are potentially left-censored. Recent adult studies suggest that to adequately model RNA pattern over age, it is necessary to account for within-subject correlation, due to repeated measures, and censoring. The aim of this study, therefore, was to establish whether it is necessary to use complex methods to allow for repeated measures within individuals and censoring of the HIV-RNA viral load in children enrolled in a cohort study. The approach involved the identification of an appropriate model for the basic pattern of RNA viral load by age and subsequent assessment of various estimation procedures accounting for repeated measures and censoring in different ways. Methods developed by Hughes involving the expectation-maximization (EM) algorithm and the Gibbs sampler were taken as the benchmark for comparison of simpler alternatives. Other approaches considered involve linear mixed-effects and ordinary least squares in which censoring is dealt with informally by taking the cut-off value as absolute or taking the mid-point between cut-off and zero. Fractional polynomials provided a substantially superior approach for modelling the dynamics of viral load over age compared to conventional polynomials or change-point models. Allowing for repeated measures was necessary to improve the power of the likelihood ratio tests required to establish the final model, but methods beyond taking the mid-point for censored values did not further improve the fit. Although Hughes' methodology is the best approach, its implementation is not necessary for the identification of the optimal model.     

Reproducibility of the blood lactate threshold, 4 mmol·l<Superscript>–1</Superscript> marker,heart rate and ratings of perceived exertion during incremental treadmill exercise in humans

The aim of this study was to investigate the reproducibility of blood lactate measurements, heart rate (HR) and ratings of perceived exertion (RPE) during treadmill exercise at speeds corresponding to the lactate threshold (v _Th,la-) and a fixed blood lactate concentration of 4 mmol·l^–1(v _la-_,4). Possible differences in reproducibility related to fitness levels were also investigated. A group of 20 men [mean (SD)] [age 20.5 (1.4) years] and 16 women [age 21.2 (0.9) years] took part in the study. The subjects performed two identical incremental exercise tests consisting of at least six 4 min stages. Blood lactate concentrations, HR and RPE were recorded at the end of each stage. Limits of agreement (LoA), correlation coefficients and 95% confidence intervals for the mean difference between tests were employed to investigate the level of agreement and reproducibility of blood lactate concentration, HR and RPE. For the group as a whole, the sample correlation coefficient for speed at v _Th,la- was r=0.88, and was r=0.92 for the speed at v _la-_,4. At v _Th,la -, the correlation coefficients for the moderately fit and unfit were r=0.94 and r=0.36, respectively, and at v _la-_,4 r=0.93 and r=0.68, respectively. The LoA for the moderately fit group indicated that a change of 1.62 km·h^–1 in v _Th,la- would be necessary to be considered a change in training status. For HR and RPE, relationships between the tests were generally poor. The LoA suggested that changes in scores must be unacceptably large. These findings cast doubt on the sensitivity of testing for change of blood lactate concentration, HR and RPE in this population. Electronic Publication     

Improvement of BMI,body composition,and body fat distribution with lifestyle modification in Japanese Americans with impaired glucose tolerance

OBJECTIVE: To determine whether diet and endurance exercise improved adiposity-related measurements in Japanese Americans with impaired glucose tolerance (IGT). RESEARCH DESIGN AND METHODS: This study compared the effects of an American Heart Association (AHA) step 2 diet (<30% of total calories as fat, <7% saturated fat, 55% carbohydrate, and < 200 mg cholesterol daily) plus endurance exercise for 1 h three times a week (treatment group) with an AHA step 1 diet (30% of total calories as fat, 10% saturated fat, 50% carbohydrate, and <300 mg cholesterol) plus stretching exercise three times a week (control group) on BMI, body composition (% fat), and body fat distribution at 6 and 24 months of follow-up in 64 Japanese American men and women with IGT, 58 of whom completed the study. RESULTS: At 6 months, the treatment group showed significantly greater reduction in percent, body fat (-1.4 +/- 0.4 vs. -0.3 +/- 0.3%); BMI (-1.1 +/- 0.2 vs. -0.4 +/- 0.1 kg/m(2)); subcutaneous fat by computed tomography at the abdomen (-29.3 +/- 4.2 vs. -5.7 +/- 5.9 cm(2)), thigh (-13.2 +/- 3.6 vs. -3.6 +/- 3.0 cm(2)), and thorax (-19.6 +/- 3.6 vs. -8.9 +/- 2.6 cm(2)); and skinfold thickness at the bicep (-2.0 +/- 0.6 vs. 1.1 +/- 0.6 mm) and tricep (-3.7 +/- 0.8 vs. -0.9 +/- 0.6 mm), which continued despite moving to home-based exercise for the last 18 months. CONCLUSIONS: Diet and endurance exercise improved BMI, body composition, and body fat distribution and, thus, may delay or prevent type 2 diabetes in Japanese Americans with IGT.     

Phasic three-dimensional impedance imaging of cardiac activity

Electrical impedance images were made using the ACT 3 instrument, which applies currents simultaneously to 32 electrodes and measures the resulting voltages on those same electrodes. A reconstruction algorithm was written for a three-dimensional cylinder having electrodes in two or four layers, using current patterns that pass current among different planes of electrodes, as well as within each plane. We have previously reported useful vertical resolution by the use of added layers of electrodes. The aim of the present study was to demonstrate that physiologically useful information can be obtained by examining cephalo-caudal differences in three-dimensional images. Phasic changes throughout the cardiac cycle are seen to be markedly different at the heart compared to lung region, both above and beside it. We formed hydrogel electrodes each 3 cm tall and 7 cm wide and applied them to the thorax of an upright human subject in four horizontal rows; each row contained eight electrodes. During breath-holding, cardiac activity was seen in all layers. With systole, conductivity in the anterior of the lowest layers decreased, but not in the upper layer. In the upper layers, conductivity increased with systole in many regions. These observations are consistent with the opposite changes in blood volume of the heart and lungs and the locations of these organs. This paper demonstrates the feasibility of producing and displaying physiologically interpretable three-dimensional images of the chest in real time.     

A 5-microm filter does not reduce propofol-induced pain

We assessed the effectiveness of a 5-microm filter in reducing propofol-induced pain and determined whether any reduction is due to removal of contaminants or an alteration in flow characteristics. A total of 120 unpremedicated women (ASA 1-3, aged 18-70 yr) were randomly allocated to one of three equal-sized groups. In group A, propofol was drawn up and injected through an unfiltered plastic cannula. In group B, propofol was drawn up through a 5-microm filter needle and injected through an unfiltered plastic cannula. In group C, propofol was drawn up and injected through a 5-microm filter needle. Unmodified propofol from a 20-ml rubber topped vial at room temperature was used. A 22-g cannula was inserted into the largest visible vein on the dorsum of the non-dominant hand. Propofol was administered at 0.5 ml.s-1 and patients were asked about pain every 10 s until unresponsive, by a blinded observer. The pain score for the patient was the taken as the most severe pain documented. The frequency and severity of pain were similar among groups. We conclude that a 5-microm filter does not reduce pain associated with injection of propofol drawn from a vial with a rubber bung.     

Current source design for electrical impedance tomography

Questions regarding the feasibility of using electrical impedance tomography (EIT) to detect breast cancer may be answered by building a sufficiently precise multiple frequency EIT instrument. Current sources are desirable for this application, yet no current source designs have been reported that have the required precision at the multiple frequencies needed. We have designed an EIT current source using an enhanced Howland topology in parallel with a generalized impedance converter (GIC). This combination allows for nearly independent adjustment of output resistance and output capacitance, resulting in simulated output impedances in excess of 2 Gohms between 100 Hz and 1 MHz. In this paper, the theoretical operation of this current source is explained, and experimental results demonstrate the feasibility of creating a high precision, multiple frequency, capacitance compensated current source for EIT applications.     

Hypoxanthine transport in human tumour cell lines: relationship to the inhibition of hypoxanthine rescue by dipyridamole

Hypoxanthine (HPX) uptake was investigated in four human tumour cell lines previously characterised as being sensitive (ds: A549 and MCF7) or insensitive (di: COR-L23 and T-47D) to dipyridamole (DP)-induced inhibition of HPX rescue from antipurine antifolate-induced growth inhibition. The aim of the study was to determine the mechanism underlying the differential sensitivity of HPX rescue to DP. The time-course of HPX uptake in the two ds cell lines was different in comparison to the two di cell lines. The initial rate of HPX uptake in the di cell lines was more rapid than in the ds cell lines such that at 60 sec the amount of HPX taken up by the former was 2-6 times higher than that taken up by the later. The K(t) and T(max) for HPX transport in di COR-L23 cells were 870 microM and 4.75 microM/10(6) cells/min and 1390 microM and 1.78 microM/10(6) cells/min in ds A549 cells. HPX transport was not sodium-dependent in these cells. Equilibrative nucleoside transporter 2 (ENT2)-mediated thymidine transport was also higher in di cells. DP inhibited HPX uptake into ds cell lines by > or =48% and by < or =20% in the di cell lines. Competition studies with HPX and thymidine transport via ENT2 indicated an overlap between nucleoside and nucleobase transport transporters in the breast cancer cell lines (MCF7 and T-47D). These studies showed that more rapid and extensive HPX uptake, as well as reduced sensitivity to DP inhibition, is associated with the inability of DP to prevent HPX rescue from antipurine antifolate-induced growth inhibition in certain human tumour cell lines.