Studying the role of vision in cycling: Critique on restricting research to fixation behaviour

In a recent study published in Accident Analysis & Prevention, Vansteenkiste et al. (2013) – as one of the first in this field – investigated the visual control of bicycle steering. They undertook the interesting task of testing cyclists’ eye fixation behaviour against Donges’ two-level model of steering, i.e. the guidance level to anticipate alternations in the course of the road and the stabilization level for lane keeping. Although the laboratory experiment itself is well conducted, we believe that its results cannot be used to test the two-level model of steering as developed for driving. The test track was only 15 m long, was completely straight and was known in advance. Accordingly, it did not provide adequate conditions for testing the guidance level. Furthermore, as the experimental lanes were much narrower than real-world cycling lanes, the stabilization level differed considerably from that in the real world. The study by Vansteenkiste et al. (2013) may provide valuable insight into the role of vision in ‘precision steering’, but, as we discuss in the paper, more elaborate research paradigms are needed to achieve more comprehensive knowledge of the role of vision in real-world cycling and cycling safety.     

Insulin-like growth factor-I and binding protein-3 in relation to childhood leukaemia

The aetiology of most cases of childhood leukaemia remains unknown, but several studies have indicated that increased birthweight and height are risk factors for the disease. Since insulin-like growth factor-I (IGF-I) mediates the effect of growth hormone and has been positively associated with prostate cancer, we have evaluated the role of this hormone and its principal binding protein, IGFBP-3, in the aetiology of childhood leukaemia. Incident cases of childhood leukaemia from those recorded by a national network of childhood oncologists were enrolled in our study. Controls were children hospitalised for acute conditions of no more than moderate severity with matching for gender, age and maternal place of residence. Blood measurements of IGF-I and IGFBP-3 were undertaken using commercially available radioimmunoassays. Serum IGF-I values decreased by about 1.7% per month, and the rate of decline was higher, though not significantly so, among cases (2.1% per month) than among controls (1.4%). There was no significant association between IGF-I and the likelihood of childhood leukaemia, but an increment of 1 microg/ml of IGFBP-3 was associated with a substantial and statistically significant reduction of childhood leukaemia by 28% (95% confidence interval 7% to 45%). Because IGFBP-3 is essentially a binding protein, we interpret our findings as indicating that bioavailable IGF-I may play an important role in the aetiology of childhood leukaemia. The much smaller quantities and the inherent instability of IGF-I in the blood in comparison to those of IGFBP-3 are likely to hinder documentation of an underlying positive association of IGF-I with the disease.     

Patch testing with budesonide in serial dilutions: the significance of dose, occlusion time and reading time

Dipeptide transporters in small intestine have a very wide substrate specificity, so that the transporter sometimes serves as a carrier for peptide-like compounds. We have synthesized dipeptide analogues conjugated at an epsilon-amino group of Lys in Val-Lys or Lys-Sar with fluorescent compounds such as fluorescein isothiocyanate and coumarin-3-carboxylic acid. Uptakes of these peptide analogues were examined by measuring intracellular accumulations into monolayers of the human intestinal epithelial cell line Caco-2 expressing the dipeptide transporter PEPT1. Kinetic analysis and effects of addition either of uncoupler (protonophore) or by Gly-Sar, one of the good substrates of PEPT1, revealed that fluorescent dipeptides were taken up by passive diffusion. In contrast, these analogues remarkably inhibited the Gly-Sar uptake by Caco-2 cells. Among the fluorescent analogues synthesized in this paper, Val-Lys(Flu) was the most potent competitive inhibitor against the Gly-Sar uptake with an inhibition constant of 5 microM. This value is the smallest among those ever reported: Val-Lys(Flu) has the highest affinity for PEPT1 among chemicals ever reported. The importance of the hydrophobic part of the substrate was pointed out.     

Mast cell activation is not required for induction of airway hyperresponsiveness by ozone in mice

Exposure to ambient ozone (O3) is associated with increased exacerbations of asthma. We sought to determine whether mast cell degranulation is induced by in vivo exposure to O3 in mice and whether mast cells play an essential role in the development of pulmonary pathophysiological alterations induced by O3. For this we exposed mast cell-deficient WBB6F1-kitW/kitW-v (kitW/kitW-v) mice and the congenic normal WBB6F1 (+/+) mice to air or to 1 or 3 parts/million O3 for 4 h and studied them at different intervals from 4 to 72 h later. We found evidence of O3-induced cutaneous, as well as bronchial, mast cell degranulation. Polymorphonuclear cell influx into the pulmonary parenchyma was observed after exposure to 1 part/milllion O3 only in mice that possessed mast cells. Airway hyperresponsiveness to intravenous methacholine measured in vivo under pentobarbital anesthesia was observed in both kitW/kitW-v and +/+ mice after exposure to O3. Thus, although mast cells are activated in vivo by O3 and participate in O3-induced polymorphonuclear cell infiltration into the pulmonary parenchyma, they do not participate detectably in the development of O3-induced airway hyperresponsiveness in mice.     

Robust and optimal use of information in stereo vision

Differences between the left and right eye's views of the world carry information about three-dimensional scene structure and about the position of the eyes in the head. The contemporary Bayesian approach to perception implies that human performance in using this source of eye-position information can be analysed most usefully by comparison with the performance of a statistically optimal observer. Here we argue that the comparison observer should also be statistically robust, and we find that this requirement leads to qualitatively new behaviours. For example, when presented with a class of stereoscopic stimuli containing inconsistent information about eccentricity of gaze, estimates of this gaze parameter recorded from one robust ideal observer bifurcate at a critical value of stimulus inconsistency. We report an experiment in which human observers also show this phenomenon and we use the experimentally determined critical value to estimate the vertical acuity of the visual system. The Bayesian analysis also provides a highly reliable and biologically plausible algorithm that can recover eye positions even before the classic stereo-correspondence problem is solved, that is, before deciding which features in the left and right images are to be matched.