Speech movements do not scale by orofacial structure size.

The potential role of a size-scaling principle in orofacial movements for speech was examined by using between-group (adults vs. 5-yr-old children) as well as within-group correlational analyses. Movements of the lower lip and jaw were recorded during speech production, and anthropometric measures of orofacial structures were made. Adult women produced speech movements of equal amplitude and velocity to those of adult men. The children produced speech movement amplitudes equal to those of adults, but they had significantly lower peak velocities of orofacial movement. Thus we found no evidence supporting a size-scaling principle for orofacial speech movements. Young children have a relatively large-amplitude, low-velocity movement strategy for speech production compared with young adults. This strategy may reflect the need for more time to plan speech movement sequences and an increased reliance on sensory feedback as young children develop speech motor control processes.     

Seasonal time constraints do not explain exceptions to the temperature size rule in ectotherms

A negative relationship between rearing temperature and adult size is widespread in ectotherms yet its causes remain poorly understood. It has been suggested that summer generations of some aquatic insects provide exceptions to this temperature size rule (TSR). The hypothesis that seasonal time constraints are responsible for these exceptions was tested using the mayfly Cloeon dipterum . Simulating early-season conditions by varying photoperiod and temperature, we found that this species followed the TSR. However, under simulated seasonal time constraints, the species omitted most of its summer adult generation (delaying completion of nymphal development till the next year), which limited the scope and applicability of the hypothesis for this species. Even those animals that completed nymphal development before winter showed no weakening of the negative temperature size relationship that was predicted by the hypothesis. Moreover, these animals did not increase rates of development or growth in response to simulated time constraints. We then analysed further the study that originally indicated aquatic insect exceptions to the TSR and suggest that gaps in the data and/or experimental design can explain the apparent exceptions. From these analyses and a survey of other exceptions, we conclude that time constraints do not account for any reported counter-TSR relationship.     

Dominant cold desert plants do not partition warm season precipitation by event size

We conducted experiments to examine the quantitative relationships between rainfall event size and rainwater uptake and use by four common native plant species of the Colorado Plateau, including two perennial grasses, Hilaria jamesii (C(4)) and Oryzopsis hymenoides (C(3)), and two shrubs, Ceratoides lanata (C(3)), and Gutierrezia sarothrae (C(3)). Specifically, we tested the hypothesis that grasses use small rainfall events more efficiently than shrubs and lose this advantage when events are large. Rainfall events between 2 and 20 mm were simulated in spring and summer by applying pulses of deuterium-labeled irrigation water. Afterwards, pulse water fractions in stems and the rates of leaf gas exchange were monitored for 9 days. Cumulative pulse water uptake over this interval (estimated by integrating the product of pulse fraction in stem water and daytime transpiration rate over time) was approximately linearly related to the amount of pulse water added to the ground in all four species. Across species, consistently more pulse water was taken up in summer than in spring. Relative to their leaf areas, the two grass species took up more pulse water than the two shrub species, across all event sizes and in both seasons, thus refuting the initial hypothesis. In spring, pulse water uptake did not significantly increase photosynthetic rates and in summer, pulse water uptake had similar, but relatively small effects on the photosynthetic rates of the three C(3) plants, and a larger effect on the C(4) plant H. jamesii. Based on these data, we introduce an alternative hypothesis for the responses of plant functional types to rainfall events of different sizes, building on cost-benefit considerations for active physiological responses to sudden, unpredictable changes in water availability.     

Classic predictions about sex change do not hold under all types of size advantage

Theory predicts that the ‘size advantage’ (rate of increase in male and female fitness with age or size) determines the direction and the timing of sex change in sequential hermaphrodites. Whereas the size advantage is generated by the mating system and would be expected to vary within and between species, the shape or form of the size advantage has rarely been estimated directly. Here, we ask whether theoretical predictions about the timing of sex change hold under different types of size advantage. We model two biological scenarios representing different processes generating the size advantage and find that different types of size advantage can produce patterns that qualitatively differ from classic predictions. Our results demonstrate that a good understanding of sequentially hermaphroditic mating systems, and specifically, a direct assessment of the processes underlying the size advantage is crucial to reliably predict and explain within‐species patterns of the timing of sex change.     

Instructions limiting the number of steps do not affect the kinetics of the threshold of balance recovery in younger adults

To our knowledge, no one has explored the effect of modifications in balance recovery instructions on the kinetics of the threshold of balance recovery. In particular, the effect of instructions limiting the number of steps on joint torques at the maximum lean angle has not been quantified. We determined the joint torques at the ankle, knee and hip of 28 younger adults recovering balance at their maximum lean angle using: (i) only a single step, (ii) no more than two steps and (iii) no limit on the number of steps. Results showed that instructions limiting the number of steps did not affect peak normalized joint torques by more than 0.0083 or 10Nm except for knee and hip flexion torques from first to second heel strike for the first step leg as well as from second toe-off to heel strike for the second step leg. However, these large differences in peak normalized joint torques after the first step were simply caused by the additional steps used when participants could take more than one step compared to when participants were limited to only a single step. Between the three limits on the number of steps, the kinetics of both legs were nearly identical up to the end of the first step and the additional steps did not help to increase the maximum lean angle. Therefore, we have demonstrated that instructions limiting or not limiting the number of steps appear to be equally valid to study falls in younger adults.     

Peroxidases do not move in phloem

Phloem exudates from grafts between Queensland Blue pumpkin (Cucurbita maxima Duch.) and Candy Red Hawkesbury watermelon (Citrullus vulgaris Schrad.) were analysed by iso-electric focusing to detect iso-enzymes of peroxidase. These enzymes did not move in intact phloem but, when stems were cut, they surged rapidly through graft unions.     

Chimpanzees know what conspecifics do and do not see

We report a series of experiments on social problem solving in chimpanzees, Pan troglodytes. In each experiment a subordinate and a dominant individual were put into competition over two pieces of food. In all experiments dominants obtained virtually all of the foods to which they had good visual and physical access. However, subordinates were successful quite often in three situations in which they had better visual access to the food than the dominant, for example, when the food was positioned so that only the subordinate (and not the dominant) could see it. In some cases, the subordinate might have been monitoring the behaviour of the dominant directly and simply avoided the food that the dominant was moving towards (which just happened to be the one it could see). In other cases, however, we ruled out this possibility by giving subordinates a small headstart and forcing them to make their choice (to go to the food that both competitors could see, or the food that only they could see) before the dominant was released into the area. Together with other recent studies, the present investigation suggests that chimpanzees know what conspecifics can and cannot see, and, furthermore, that they use this knowledge to devise effective social-cognitive strategies in naturally occurring food competition situations. Copyright 2000 The Association for the Study of Animal Behaviour.     

Seed number and environmental conditions do not explain seed size variability for the invasive herb Lupinus polyphyllus

Intraspecific variation in seed size may result from life-history constraints or environmental conditions experienced. This variation in seed size is likely to affect the early stage of invasion as seed size may contribute to the success or failure of population establishment. However, only a few studies have examined seed size variability and its causes and consequences for invaders so far. Using the invasive herb Lupinus polyphyllus, we estimated seed mass variation within and among 39 populations from two different geographic regions in a part of the invaded range. We empirically and experimentally evaluated the effect of seed number and environmental conditions (e.g. geographic region, habitat type, intraspecific competition) on seed mass, emergence and seedling performance. Seed mass varied threefold, being largest among individual plants within populations and smallest among populations. Variation in seed mass was neither related to seed number nor the environmental conditions examined, but led to differences in offspring performance, with emergence and seedling size increasing with seed mass. Larger L. polyphyllus seeds were better establishers than smaller seeds regardless of environmental conditions, indicating that the success of L. polyphyllus invasions is likely to depend positively on seed mass. Our results suggest that some plant species such as the invasive L. polyphyllus may not show an adaptive response in seed mass to resources or environmental conditions, which may partly explain their ability to colonise a range of different habitats.     

An alternate model of thyroid cytology: practical not perfect

A sample of 384 thyroid cytology specimens prepared by cytospin over a 2.5-year period was classified by original report into inadequate, non-neoplastic and suspicious of neoplasia or worse. This was then compared with subsequent histology. The resulting data showed an inadequacy rate of 33%, a sensitivity of 55%, a specificity of 59%, a positive predictive value of 64% and a negative predictive value of 93%. On review of the cytology, in knowledge of the subsequent histology, the maximum achievable results were determined to have a positive predictive value of 79% and a negative predictive value of 97%. No clinically significant adverse event was detected.     

Occlusion junctions do not improve stereoacuity

Occlusion geometry gives rise to interocular shifts in the positions of binocularly viewed contour junctions. Since these shifts do not give rise to normal binocular disparities, they have been called 'pseudodisparities'. Previous work has shown that the unmatched contour segments of a partially occluded contour at occlusion junctions can be used to recover the geometry of the occluding surface through the construction of 'illusory' contours. Here, experiments were performed to determine whether such junction shifts could enhance stereoscopic depth detection when the relative disparity between the contours was below threshold. Our results showed that stereoscopic depth detection does not improve when pseudodisparity is present. We conclude that the visual system is less sensitive to pseudodisparity than to conventional disparity information. We suggest that the primary role of pseudodisparity is to overcome conditions of camouflage.     

Tumor cells do not arise frequently

Summary A hypothesis greatly influencing thinking and experimental work in tumor immunology is that many tumor cells arise daily in an organism. However, relatively low numbers of tumours become clinically manifest. This discrepancy has intially led to the hypothesis that the great majority of these potential tumors is killed by immune surveillance mechanisms. After some time, however, serious objections were raised against this function of the immune system. When the interest in immune surveillance faded away, investigators started to study natural resistance against the de novo arising tumor cells. In this paper the data on natural resistance (and immune surveillance) are reviewed. These data lead to the conclusion than an efficient natural resistance that could kill many de novo arising tumor cells is lacking. Taken together the data suggest that no tumors arise when immune surveillance and/or natural resistance are absent. This implies that tumor cells probably do not arise frequently. Acceptance of this conclusion leads to a reappraisal of the role of immune surveillance and natural resistance against tumor cells. This reappraisal will mean a shift from (a) the hypothesized failsafe mechanisms to (b) mechanisms that may or may not kill rarely arising tumor cells, depending for instance on the antigenicity of the tumor cells and their sensitivity to tumoricidal mechanisms.