Negotiating left-hand and right-hand bends: a motorcycle simulator study to investigate experiential and behaviour differences across rider groups

Why do motorcyclists crash on bends? To address this question we examined the riding styles of three groups of motorcyclists on a motorcycle simulator. Novice, experienced and advanced motorcyclists navigated a series of combined left and right bends while their speed and lane position were recorded. Each rider encountered an unexpected hazard on both a left- and right-hand bend section. Upon seeing the hazards, all riders decreased their speed before steering to avoid the hazard. Experienced riders tended to follow more of a racing line through the bends, which resulted in them having to make the most severe changes to their position to avoid a collision. Advanced riders adopted the safest road positions, choosing a position which offered greater visibility through the bends. As a result, they did not need to alter their road position in response to the hazard. Novice riders adopted similar road positions to experienced riders on the left-hand bends, but their road positions were more similar to advanced riders on right-hand bends, suggesting that they were more aware of the risks associated with right bends. Novice riders also adopted a safer position on post-hazard bends whilst the experienced riders failed to alter their behaviour even though they had performed the greatest evasive manoeuvre in response to the hazards. Advanced riders did not need to alter their position as their approach to the bends was already optimal. The results suggest that non-advanced riders were more likely to choose an inappropriate lane position than an inappropriate speed when entering a bend. Furthermore, the findings support the theory that expertise is achieved as a result of relearning, with advanced training overriding ‘bad habits’ gained through experience alone.     

Mechanics of increased support of weight by the hindlimbs in primates

Quadrupedal primates support most of their weight on their hindlimbs during locomotion. Neither the position of their center of gravity nor the average position of their foot contacts is substantially different from that of other quadrupeds supporting most of their weight on their forelimbs. Arguments are presented to support the theory that high levels of hindlimb retractor activity will produce this shift of support to the hindlimbs. If this muscular activity is appropriately timed, it will generate only low horizontal accelerations, which can be offset by small changes in the average position of the limbs. Estimates of muscular force are derived from force plate and kinematic data, which indicate that primates in fact do exhibit the postulated pattern of muscular activity. It is suggested that this shift occurs to reduce the compressive forces on the forelimbs.     

Heart position in snakes: response to "phylogeny, ecology, and heart position in snakes"

Here we comment on a recent article (Gartner et al. 2010 ) that addresses previous adaptive interpretations of heart position in the context of gravity effects on blood circulation of snakes. The authors used phylogenetically based statistical methods and concluded that both habitat and phylogeny influence heart position, which they contend is relatively more posterior in arboreal compared to terrestrial species. Their result is based on measurements of heart position relative to snout-vent length, rather than total body length as in previous studies. However, gravity acts on the total length of the arterial-venous vasculature, and caudal segments of continuous blood columns cannot be ignored. Arboreal snakes have relatively long tails; therefore anterior hearts appear to be more "posterior" when the position is described relative to a shorter trunk. There is no physiologically valid explanation for the alleged posterior heart position in arboreal snakes, and multiple lines of published evidence to the contrary are ignored. The authors secondarily evaluated their data set with estimates for total body length based on measurements from other taxa. They found no statistical difference between heart position in arboreal versus terrestrial species, yet their article implied otherwise. Gartner et al. ( 2010 ) contrasted "aquatic" and terrestrial species throughout their paper, and they claimed there is no correlation between heart position and habitat among "aquatic and terrestrial species." But they did not include any aquatic species in their data set. Therefore, the article confuses rather than promotes understanding of cardiovascular adaptation to gravity.     

Accuracy of Self-Reported Sleep Position in Late Pregnancy

Background

There is emerging research to suggest that supine maternal sleep position in late pregnancy may adversely affect fetal wellbeing. However, these studies have all been based on maternal report of sleeping position. Before recommendations to change sleep position can be made it is important to determine the validity of these studies by investigating how accurate pregnant women are in reporting their sleep position. If avoiding the supine sleeping position reduces risk of poor pregnancy outcome, it is also important to know how well women can comply with the instruction to avoid this position and sleep on their left.

Method

Thirty women in late pregnancy participated in a three-night observational study and were asked to report their sleeping position. This was compared to sleep position as recorded by a night capable video recording. The participants were instructed to settle to sleep on their left side and if they woke overnight to settle back to sleep on their left.

Results

There was a moderate correlation between reported and video-determined left-side sleep time (r = 0.48), mean difference = 3 min (SD = 3.5 h). Participants spent an average of 59.60% (SD = 16.73%) of time in bed on their left side (ICC across multiple nights = 0.67). Those who included left side among their typical sleep positions reported significantly longer sleep during the study (p<0.01).

Conclusions

On average participant reports of sleep position were relatively accurate but there were large individual differences in reporting accuracy and in objectively-determined time on left side. Night-to-night consistency was substantial. For those who do not ordinarily sleep on that side, asking participants to sleep on their left may result in reduced sleep duration. This is an important consideration during a sleep-critical time such as late pregnancy.     

Stereopsis and the random element in the organization of the striate cortex.

Receptive field position and orientation disparities are both properties of binocularly discharged striate neurons. Receptive field position desparities have been used as a key element in the neural theory for binocular depth discrimination. Since most striate cells in the cat are binocular, these position disparities require that cells immediately adjacent to one another in the cortex should show a random scatter in their monocular receptive field positions. Superimposed on the progressive topographical representation of the visual field on the striate cortex there is experimental evidence for a localized monocular receptive field position scatter. The suggestion is examined that the binocular position disparities are built up out of the two monocular position scatters. An examination of receptive field orientation disparities and their relation to the random variation in the monocular preferred orientations of immediately adjacent striate neurons also leads to the conclusion that binocular orientation disparities are a consequence of the two monocular scatters. As for receptive field position, the local scatter in preferred orientation is superimposed on a progressive representation of orientation over larger areas of the cortex. The representation in the striate cortex of visual field position and of stimulus orientation is examined in relation to the correlation between the disparities in receptive field position and preferred orientation. The role of orientation disparities in binocular vision is reviewed.     

Leaf traits and herbivory rates of tropical tree species differing in successional status

We evaluated leaf characteristics and herbivory intensities for saplings of fifteen tropical tree species differing in their successional position. Eight leaf traits were selected, related to the costs of leaf display (specific leaf area [SLA], water content), photosynthesis (N and P concentration per unit mass), and herbivory defence (lignin concentration, C:N ratio). We hypothesised that species traits are shaped by variation in abiotic and biotic (herbivory) selection pressures along the successional gradient. All leaf traits varied with the successional position of the species. The SLA, water content and nutrient concentration decreased, and lignin concentration increased with the successional position. Herbivory damage (defined as the percentage of damage found at one moment in time) varied from 0.9-8.5% among the species, but was not related to their successional position. Herbivory damage appeared to be a poor estimator of the herbivory rate experienced by species, due to the confounding effect of leaf lifespan. Herbivory rate (defined as percentage leaf area removal per unit time) declined with the successional position of the species. Herbivory rate was only positively correlated to water content, and negatively correlated to lignin concentration, suggesting that herbivores select leaves based upon their digestibility rather than upon their nutritive value. Surprisingly, most species traits change linearly with succession, while resource availability (light, nutrients) declines exponentially with succession.     

Intraspecies diversity of the industrial yeast strains Saccharomyces cerevisiae and Saccharomyces pastorianus based on analysis of the sequences of the internal transcribed spacer (ITS) regions and the D1/D2 region of 26S rDNA

We divided industrial yeast strains of Saccharomyces cerevisiae into three groups based on the sequences of their internal transcribed spacer (ITS) regions. One group contained sake yeasts, shochu yeasts, and one bakery yeast, another group contained wine yeasts, and the third group contained beer and whisky yeasts, including seven bakery yeasts. The three groups were distinguished by polymorphisms at two positions, designated positions B and C, corresponding to nucleotide numbers 279 and 301 respectively in the S288C strain. The yeasts in the Japanese group had one thymine at position B and one thymine at position C. The wine yeasts had one thymine at position B and one cytosine at position C. And the beer and whisky yeasts had two thymines at position B and one cytosine at position C. Strains of S. pastorianus were divided into three groups based on the sequences of their 26S rDNA D1/D2 and ITS regions.     

Neuronal processing delays are compensated in the sensorimotor branch of the visual system

Moving objects change their position until signals from the photoreceptors arrive in the visual cortex. Nonetheless, motor responses to moving objects are accurate and do not lag behind the real-world position. The questions are how and where neural delays are compensated for. It was suggested that compensation is achieved within the visual system by extrapolating the position of moving objects. A visual illusion supports this idea: when a briefly flashed object is presented in the same position as a moving object, it appears to lag behind. However, moving objects do not appear ahead of their final or reversal points. We investigated a situation where participants localized the final position of a moving stimulus. Visual perception and short-term memory of the final target position were accurate, but reaching movements were directed toward future positions of the target beyond the vanishing point. Our results show that neuronal latencies are not compensated for at early stages of visual processing, but at a late stage when retinotopic information is transformed into egocentric space used for motor responses. The sensorimotor system extrapolates the position of moving targets to allow for precise localization of moving targets despite neuronal latencies.     

Unusual sensory setae of the raptorial Branchinecta gigas (Branchiopoda: Anostraca)

In many vernal pools, visibility is very poor because of the turbidity from suspended clay particles. For predatory species like Branchinecta gigas, these conditions can be detrimental to successful prey capture. In vernal lakes in central California, B. gigashave developed specialized hunting modes to capture anostracan prey in pools of low visibility. The position of their body, the kinematics of their locomotion, and their reduced eye size suggested the possibility of novel sensory structures on their antennae and/or their cercopods designed to enhance their prey capture abilities. Using Scanning Electron Microscopy, we investigated the presence and design of sensory setae on the antennae and cercopods of B. gigas. On both males and females, there are dense patches of sensilla along the length of the antennae. They are oriented ventrally and slightly anteriorly. These antennal setae appear to be chemosensory in structure and position; they resemble antennal setae of other branchiopods. However, the setae of the cercopods are unusual in their morphology and location on the appendage. The cercopods, which are bent over the head in the hunting position, have a linear arrangement of specialized setae on their ventral side. They are jointed setae with an anterior crown of protective spines. The setal joint only permits limited abduction either toward the head in the hunting position or ventrally when swimming. These setae appear to be mechanosensory in function and may be adaptations to a raptorial lifestyle. They correlate well with the behavioral components of hunting in B. gigasand their complex prey capture mechanism.     

雷蒙德氏棉和拟南芥基因启动子中顺式作用元件的分布

随着雷蒙德氏棉(Gossypium raimondii)基因组草图的完成, 相关的基因组学研究已经全面展开。文章利用已公布的雷蒙德氏棉和拟南芥基因组序列, 结合顺式作用元件(cis-regulatory element, CRE)数据库PLACE中的CRE序列信息, 对两个物种中带有5′UTR注释的基因启动子上游1 000 bp序列进行CRE扫描和统计。结果表明, 雷蒙德氏棉和拟南芥基因组中分别有44(12.3%)和57(15.5%)个CRE在启动子的特定位置呈峰状分布, 其中在两个基因组均呈峰状分布的有34个, 这些CRE又可以根据核心序列分为4大类。TATABOX类CRE顶峰在启动子中出现的位置和其真实位置(~ -30 bp)具有一致性, 预示CRE真实位置在不同基因启动子中相对保守, 从而推测本研究中呈峰状分布CRE的顶峰位置可能就是转录因子和该CRE结合的真实位置。而同一CRE在两个基因组中存在的位置差异则主要源于雷蒙德氏棉基因的5′UTR长度变异大于拟南芥。另外, 文章还发现绝大多数峰状分布的CRE的位置都集中在-110 bp~0 bp之间, 这种集中的分布可能更有利于转录因子之间相互作用, 从而调控下游基因的表达。     

Function and position determine relative proportions of different fiber types in limb muscles of the lizard Tropidurus psammonastes

Skeletal muscles can be classified as flexors or extensors according to their function, and as dorsal or ventral according to their position. The latter classification evokes their embryological origin from muscle masses initially divided during limb development, and muscles sharing a given position do not necessarily perform the same function. Here, we compare the relative proportions of different fiber types among six limb muscles in the lizard Tropidurus psammonastes. Individual fibers were classified as slow oxidative (SO), fast glycolytic (FG) or fast oxidative-glycolytic (FOG) based on mitochondrial content; muscles were classified according to position and function. Mixed linear models considering one or both effects were compared using likelihood ratio tests. Variation in the proportion of FG and FOG fibers is mainly explained by function (flexor muscles have on average lower proportions of FG and higher proportions of FOG fibers), while variation in SO fibers is better explained by position (they are less abundant in ventral muscles than in those developed from a dorsal muscle mass). Our results clarify the roles of position and function in determining the relative proportions of the various muscle fibers and provide evidence that these factors may differentially affect distinct fiber types.     

Adaptive control of center of mass (global) motion and its joint (local) origin in gait

Dynamic gait stability can be quantified by the relationship of the motion state (i.e. the position and velocity) between the body center of mass (COM) and its base of support (BOS). Humans learn how to adaptively control stability by regulating the absolute COM motion state (i.e. its position and velocity) and/or by controlling the BOS (through stepping) in a predictable manner, or by doing both simultaneously following an external perturbation that disrupts their regular relationship. Post repeated-slip perturbation training, for instance, older adults learned to forward shift their COM position while walking with a reduced step length, hence reduced their likelihood of slip-induced falls. How and to what extent each individual joint influences such adaptive alterations is mostly unknown. A three-dimensional individualized human kinematic model was established. Based on the human model, sensitivity analysis was used to systematically quantify the influence of each lower limb joint on the COM position relative to the BOS and the step length during gait. It was found that the leading foot had the greatest effect on regulating the COM position relative to the BOS; and both hips bear the most influence on the step length. These findings could guide cost-effective but efficient fall-reduction training paradigm among older population.     

Mapping adenosine cyclic 3',5'-phosphate binding sites on type I and type II adenosine cyclic 3',5'-phosphate dependent protein kinases using ribose ring and cyclic phosphate ring analogues of adenosine cyclic 3',5'-phosphate

A series of adenosine cyclic 3',5'-phosphate (cAMP) derivatives containing modifications or substitutions in either the 2',3',4', or 5' position or the phosphate were examined for their abilities to activate type I isozymes of cAMP-dependent protein kinase (PK I) from rabbit or porcine skeletal muscle and type II isozymes of cAMP-dependent protein kinase (PK II) from bovine brain and heart. The studies revealed that the activation of both PK I and PK II isozymes requires a 2'-hydroxyl group in the ribo configuration, a 3' oxygen in the ribo configuration, and a charged cyclic phosphate. The two isozymes appeared to differ in those portions of their respective cAMP-binding sites that are adjacent to the 4' position of the ribose ring and the 3' position, 5' position, and phosphate portion of the cyclic phosphate ring.     

Cytochrome P4501A1 polymorphisms in the Amerindian and Mestizo populations of Mexico

Several polymorphisms in the CYP1A1 locus have been identified and their genotypes appear to exhibit population frequencies that depend on ethnicity. We studied two CYP1A1 polymorphic sites (position 4889 and 6235) in a group of 212 unrelated healthy individuals belonging to three different Mexican populations (106 Mexican Mestizos, 52 Teenek and 54 Mayos). Comparison among Mexican populations showed increased frequency of the *Ile allele (A on position 4889) in Mexican Mestizos when compared to Amerindians (p < 0.05). The analysis of position 6235 showed increased frequencies of *m2 (C in this position) allele in Teenek when compared to Mestizos and Mayos (p < 0.05) and of *m2/*m2 genotype when compared to Mestizos (p < 0.05). Amerindian populations (from Mexico and South America) presented the lowest frequencies of *Ile (position 4889) and *m1 (position 6235) alleles, however these frequencies vary according to the ethnic group studied. Mexican Amerindian groups together with other South Amerindian populations showed the highest frequencies for *Val at position 4889 and the *m2 allele at position 6235. The present study corroborates the high frequencies of*Val and *m2 alleles in the Amerindian populations and detects some differences between Mexican populations that correlate with linguistic differences. Our data could be helpful in understanding the distribution of these polymorphisms and in clarifying their roles as genetic and evolution markers in Amerindian populations.     

Patterns of spinal sensory-motor connectivity prescribed by a dorsoventral positional template

Sensory-motor circuits in the spinal cord are constructed with a fine specificity that coordinates motor behavior, but the mechanisms that direct sensory connections with their motor neuron partners remain unclear. The dorsoventral settling position of motor pools in the spinal cord is known to match the distal-to-proximal position of their muscle targets in the limb, but the significance of invariant motor neuron positioning is unknown. An analysis of sensory-motor connectivity patterns in FoxP1 mutant mice, where motor neuron position has been scrambled, shows that the final pattern of sensory-motor connections is initiated by the projection of sensory axons to discrete dorsoventral domains of the spinal cord without regard for motor neuron subtype or, indeed, the presence of motor neurons. By implication, the clustering and dorsoventral settling position of motor neuron pools serve as a determinant of the pattern of sensory input specificity and thus motor coordination.     

Mu receptor binding of some commonly used opioids and their metabolites.

The binding affinity to the mu receptor of some opioids chemically related to morphine and some of their metabolites was examined in rat brain homogenates with 3H-DAMGO. The chemical group at position 6 of the molecule had little effect on binding (e.g. morphine-6-glucuronide Ki = 0.6 nM; morphine = 1.2 nM). Decreasing the length of the alkyl group at position 3 decreased the Ki values (morphine less than codeine less than ethylmorphine less than pholcodine). Analgesics with high clinical potency containing a methoxyl group at position 3 (e.g. hydrocodone, Ki = 19.8 nM) had relatively weak receptor binding, whilst their O-demethylated metabolites (e.g. hydromorphone, Ki = 0.6 nM) had much stronger binding. Many opioids may exert their pharmacological actions predominantly through metabolites.     

Effect of Leaf Age and Nodal Position on Receptivity of Rice Leaves to Infection by Pyricularia grisea

The effect of leaf age and nodal position on leaf receptivity to rice blast, caused by Pyricularia grisea , was studied by inoculating potted Rosemont plants with blast pathogen race IC-17, isolate 92T107. at different growth stages. Regressioti equations were used to describe the effect ofleaf age (degree days > 10 C) and nodal position on lesion density, the relative frequency of lesion appearance, and the lesion area distribtition. The number of sporulating lesions per cm² of inoculated leaf area was highest for leaves inoculated early in their development and progressively lower for leaves inoculated later in their development. The average lesion density for less than 1-day-old leaves at nodal position 6 was about four times the density for 10-day-old leaves of the same nodal position. Lesion density was similar for leaves of less than 1-day-old from the 4th to the 7th nodal position, but dropped sharply from the 7th to the 11 th nodal position. The flag leaf was the least susceptible of all nodal positions. The average lesion density for young leaves of about 1-day-old at nodal position 6 was about 27 times the density for young flag leaves of the same age. The incubation period increased with leaf age. but was not obviously affected by leaf nodal position. Lesion area increased linearly with time, but was not affected by leaf age and nodal position. The results are of use for epidemiological investigations which rely on detailed quantitative leaf susceptibility data for accurate blast forecasts.     

Impairment of proprioception after whiplash injury

Whiplash injury usually occurs in traffic accidents. Persons experienced this injury might have an impairment of proprioception clinically expressed as inability to determine the exact position of their heads. The aim of this study was to examine the loss of proprioception in people who had a whiplash injury. The study included 60 subjects with cervical spine injury, aged 20 to 50 years and 60 healthy volunteers matched by sex and age. The instrument used for cervical spine mobility assessment was the Cervical Measurement System (CMS), which determines the ability of subjects to return their head in the exact position as it was before they turned it 30 degrees left or right. Patients with cervical spine injury showed significant impairment of proprioception in comparison with healthy subjects (P < 0.001). The results support the hypothesis that subject with recent cervical spine injury have incorrect perception of their head position. Therefore, their rehabilitation should include the correction of proprioception and head coordination.     

Purification and primary structure determination of two Bowman-Birk type trypsin isoinhibitors from Cratylia mollis seeds

Two Bowman-Birk type trypsin inhibitors (CmTI(1) and CmTI(2)) were purified from Cratylia mollis seeds by acetone precipitation, ion exchange, gel filtration and reverse-phase chromatography. CmTI(1) and CmTI(2), with 77 and 78 amino acid residues, respectively, were sequenced in their entirety and show a high structural similarity to Bowman-Birk inhibitors from other Leguminosae. The putative reactive sites of CmTI(1) are a lysine residue at position 22 and a tyrosine residue at position 49. Different reactive sites, as identified by their alignment with related inhibitors, were found for CmTI(2): lysine at position 22 and leucine at position 49. The dissociation constant K(i) of the complex with trypsin is 1.4 nM. The apparent molecular mass is 17 kDa without DDT and 11 kDa with reducing agent and heating.     

Relations between the errors of targeted movements and inexactitude of visual perception of space

Errors of targeted movements of the arm to the places of presentation of light targets (in darkness) were studied in healthy subjects kept in a vertical position or laying on their backs. An error along theY axis (corresponding to the longitudinal body axis) changed its sign depending on the body orientation with respect to the gravitation vector. In the vertical position, the arm shifted to the feet at the movement’s termination, while in the laying position it shifted to the head. AnX error showed no dependence on the position of the body in space. The errors reached their maxima in the absence of visual control, but became two-three times smaller when the tested subject could observe the position of an indicator (light diodes) fixed on the end of the index finger (or of a pointer rod). When the spatial positions of targets were reconstructed according to verbal “indications”, the amplitudes ofX andY errors appeared similar to those at real movements (indication under visual control). In this case, the sign ofY errors also depended on the body orientation, but their direction was opposite. We suppose that systematicY errors at the targeted arm movements are determined not only by an antigravitation component of the motor program, but also by shifting of a sensory visual estimations of the spatial target position.