Head activator and head inhibitor are signals for nerve cell differentiation in hydra

Head activator and head inhibitor control nerve cell differentiation in hydra. Head activator acts as a stimulatory signal on nerve cell differentiation by forcing nerve cell precursors, which are arrested before final differentiation, to develop into mature nerve cells. Head inhibitor acts antagonistically by keeping the cells in their arrested state, before mitosis and terminal differentiation. This and other evidence suggest that the arrest of the nerve cell precursors occurs in the G₂-phase of their cell cycle. Nerve cell differentiation can also be induced by wounding the animal. This is a consequence of an initial disinhibition caused by diffusion of head inhibitor out of the tissue and the subsequent release of head activator which then stimulates nerve cell differentiation.     

Proposing a Radial Basis Function and CSDM Indices to Predict the Traumatic Brain Injury Risk

BackgroundMany head injury indices and finite element (FE) head models have been proposed to predict traumatic brain injury (TBI). Although FE head models are suitable methods with high accuracy, they are computationally intensive. Head motion-based brain injury criteria are usually fast tools with lower accuracy. So, the objective of this study is to propose new criteria along with an artificial neural network model to predict TBI risks, which can be fast and accurate.MethodsFor this purpose, 250 FE head simulations have been carried out at 5 magnitudes and 50 rotational impact directions using the SIMon model. The effects of directions and magnitudes of rotational impacts were assessed for cumulative strain damage measure (CSDM) values. Next, statistical analysis and neural network were applied to predict CSDM values.ResultsThe results of the present research showed that the direction of rotation in the sagittal and frontal planes had a considerable effect on the CSDM values. Furthermore, new brain injury indices and a radial basis function neural network have been proposed to predict CSDM values which having high correlation coefficients with SIMon responses.ConclusionsThe results of this research demonstrated that rotational impact directions should be used to develop new head injury criteria being able to predict CSDM values. However, findings of present research proved that head motion-based brain injury criteria and RBF network can be used to predict FE head model responses with high speed and accuracy.     

The new head hypothesis revisited

In 1983, a new theory, the New Head Hypothesis, was generated within the context of the Tunicate Hypothesis of deuterostome evolution. The New Head Hypothesis comprised four claims: (1) neural crest, neurogenic placodes, and muscularized hypomere are unique to vertebrates, (2) the structures derived from these tissues allowed a shift from filter feeding to active predation, (3) the rostral head of vertebrates is a neomorphic unit, and (4) neural crest and neurogenic placodes evolved from the epidermal nerve plexus of ancestral deuterostomes. These claims are re-examined within the context of evolutionary developmental biology. The first may or may not be valid, depending on whether protochordates have these tissues in rudimentary form. Regarding the second, clearly, the elaboration of these tissues in vertebrates is correlated with a shift from filter feeding to active predation. The third claim is clarified, i.e., that the elaboration of the alar portion of the rostral brain and the development of olfactory organs and their associated connective tissues represent a neomorphic unit, which appears to be valid. The fourth is rejected. When the origin of neural crest and neurogenic placodes is examined within the context of developmental biology, it appears they evolved due to the rearrangement of germ layers in the blastulae of the deuterostomes that gave rise to chordates. Deuterostome evolution and the origin of vertebrates are also re-examined in the context of new data from developmental biology and taxonomy. The Tunicate Hypothesis is rejected, and a new version of the Dipleurula Hypothesis is presented.     

On the barn owl’s visual pre-attack behavior: I. Structure of head movements and motion patterns

Barn owls exhibit a rich repertoire of head movements before taking off for prey capture. These movements occur mainly at light levels that allow for the visual detection of prey. To investigate these movements and their functional relevance, we filmed the pre-attack behavior of barn owls. Off-line image analysis enabled reconstruction of all six degrees of freedom of head movements. Three categories of head movements were observed: fixations, head translations and head rotations. The observed rotations contained a translational component. Head rotations did not follow Listing’s law, but could be well described by a second-order surface, which indicated that they are in close agreement with Donder’s law. Head translations did not contain any significant rotational components. Translations were further segmented into straight-line and curved paths. Translations along an axis perpendicular to the line of sight were similar to peering movements observed in other animals. We suggest that these basic motion elements (fixations, head rotations, translations along a straight line, and translation along a curved trajectory) may be combined to form longer and more complex behavior. We speculate that these head movements mainly underlie estimation of distance during prey capture.     

The phenomenon of debrachycephalization in Jena school children

Head measurements are performed within the anthropological investigations of school children from Jena (Germany) since more than 5 decades (1944-1995). Here we report on secular changes of the head length, the head breadth and the cephalic index. The head circumference, measured in 1985 and in 1995, is included in the analysis. Head length and head breadth show a contrary development over the whole period: the average length of the head increases between the consecutive investigations, whereas the breadth of the head decreases continuously between the separate investigations. As a consequence the cephalic index decreases in boys and girls for about 8 units since 1944. In this way a secular change of the shape of the head in the sense of debrachycephalisation can be proved in Jena school children. The head circumference, however, remains nearly constant between 1985 and 1995. Possible causes of this process of debrachycephalisation are focussed in this article.     

Study on the heredity of the head size in fifty Punjabi families

An attempt has been made to study the inheritance of the size or the Inrgeness of the head as suggested by the value of the Cephalic module or Head module. The material for the present study consists of 50 families with 76 adult offspring and 12 pairs of twins (4 MZ and 8 DZ pairs). The largeness of the head is dependent to a large extent on the individual parts of the cranium and it may be fairly assumed that the individual parts of the cranium are determined by hereditary factors, may be polygenic in nature, which are controlling their growth and development, though environment also plays its role. Presently it is not possible to ascertain the exact mode of inheritance of the head size, nevertheless, it may be stated that the size or the largeness of the head as represented by the Cephalic module is determined by polygenes in all probability with additive effects, which are too small to be traced.     

基于外部形态特征量化分析判别菱角水螟幼虫龄期

【目的】本实验拟为田间准确快速判别菱角水螟Parapoynx crisonalis(Walker)幼虫龄期提供一种新方法,以便监测其发生规律、预测其发生时间。【方法】本研究通过对幼虫头壳宽、复眼距、体宽和体长4项外部形态指标的测量,运用Crosby生长法则和线性回归分析方法,结合各项指标的频次分布进行分析。【结果】各龄幼虫头壳宽平均值的变异系数和Crosby指数最小,为判别幼虫龄期的最佳分龄指标,幼虫期共分为5龄,1~5龄的头壳宽分别为(0.2493±0.0053)、(0.3454±0.0018)、(0.5079±0.0031)、(0.7419±0.0190)和(1.1287±0.0369)mm,其与龄期数呈线性关系。通过实验室饲养观察菱角水螟幼虫蜕皮次数验证该虫幼虫期分为5个龄期。【结论】头壳宽为判定菱角水螟幼虫龄期的最佳指标,复眼距次之。     

The response of the pediatric head to impacts onto a rigid surface

The study of pediatric head injury relies heavily on the use of finite element models and child anthropomorphic test devices (ATDs). However, these tools, in the context of pediatric head injury, have yet to be validated due to a paucity of pediatric head response data. The goal of this study is to investigate the response and injury tolerance of the pediatric head to impact.Twelve pediatric heads were impacted in a series of drop tests. The heads were dropped onto five impact locations (forehead, occiput, vertex and right and left parietal) from drop heights of 15 and 30 cm. The head could freely fall without rotation onto a flat 19 mm thick platen. The impact force was measured using a 3-axis piezoelectric load cell attached to the platen.Age and drop height were found to be significant factors in the impact response of the pediatric head. The head acceleration (14%–15 cm; 103–30 cm), Head Injury Criterion (HIC) (253%–15 cm; 154%–30 cm) and impact stiffness (5800%–15 cm; 3755%–30 cm) when averaged across all impact locations increased with age from 33 weeks gestation to 16 years, while the pulse duration (66%–15 cm; 53%–30 cm) decreased with age. Increases in head acceleration, HIC and impact stiffness were also observed with increased drop height, while pulse duration decreased with increased drop height.One important observation was that three of the four cadaveric heads between the ages of 5-months and 22-months sustained fractures from the 15 cm and 30 cm drop heights. The 5-month-old sustained a right parietal linear fracture while the 11- and 22-month-old sustained diastatic linear fractures.     

Helmet liner evaluation to mitigate head response from primary blast exposure

Head injury resulting from blast loading, including mild traumatic brain injury, has been identified as an important blast-related injury in modern conflict zones. A study was undertaken to investigate potential protective ballistic helmet liner materials to mitigate primary blast injury using a detailed sagittal plane head finite element model, developed and validated against previous studies of head kinematics resulting from blast exposure. Five measures reflecting the potential for brain injury that were investigated included intracranial pressure, brain tissue strain, head acceleration (linear and rotational) and the head injury criterion. In simulations, these measures provided consistent predictions for typical blast loading scenarios. Considering mitigation, various characteristics of foam material response were investigated and a factor analysis was performed which showed that the four most significant were the interaction effects between modulus and hysteretic response, stress–strain response, damping factor and density. Candidate materials were then identified using the predicted optimal material values. Polymeric foam was found to meet the density and modulus requirements; however, for all significant parameters, higher strength foams, such as aluminum foam, were found to provide the highest reduction in the potential for injury when compared against the unprotected head.     

Injury-induced activation of the MAPK/CREB pathway triggers apoptosis-induced compensatory proliferation in hydra head regeneration

After bisection, Hydra polyps regenerate their head from the lower half thanks to a head-organizer activity that is rapidly established at the tip. Head regeneration is also highly plastic as both the wild-type and the epithelial Hydra (that lack the interstitial cell lineage) can regenerate their head. In the wild-type context, we previously showed that after mid-gastric bisection, a large subset of the interstitial cells undergo apoptosis, inducing compensatory proliferation of the surrounding progenitors. This asymmetric process is necessary and sufficient to launch head regeneration. The apoptotic cells transiently release Wnt3, which promotes the formation of a proliferative zone by activating the beta-catenin pathway in the adjacent cycling cells. However the injury-induced signaling that triggers apoptosis is unknown. We previously reported an asymmetric immediate activation of the mitogen-activated protein kinase/ribosomal S6 kinase/cAMP response element binding protein (MAPK/RSK/CREB) pathway in head-regenerating tips after mid-gastric bisection. We show here that pharmacological inhibition of the MAPK/ERK pathway or RNAi knockdown of the RSK, CREB, CREB binding protein (CBP) genes prevents apoptosis, compensatory proliferation and blocks head regeneration. As the activation of the MAPK pathway upon injury plays an essential role in regenerating bilaterian species, these results suggest that the MAPK-dependent activation of apoptosis-induced compensatory proliferation represents an evolutionary-conserved mechanism to launch a regenerative process.     

甘蓝耐裂球性评价方法研究及种质鉴定筛选

裂球是甘蓝生产中存在的一个严重问题。本研究通过对7份春甘蓝和8份秋甘蓝不同耐裂性材料的田间裂球方式、裂球率、裂球程度比较,综合最大裂口层数、裂口面积,建立了甘蓝耐裂球性评价方法并制定了甘蓝个体裂球分级标准。根据春甘蓝叶球成熟后5天、秋甘蓝叶球成熟后15天的裂球指数将甘蓝种质群体的耐裂球性分为极耐裂球、耐裂球、中耐裂球、易裂球、极易裂球5级。对59份春、秋甘蓝种质进行耐裂球性鉴定筛选获得一批极耐裂甘蓝种质资源。同时,对甘蓝室内成熟叶球浸泡法评价耐裂球性进行了初探。首次提出室内浸泡能够准确的鉴定甘蓝的耐裂球性,可用于选育耐裂球品种及生产实践。通过本研究制定出一套春、秋甘蓝耐裂球性的田间及室内鉴定方法与标准,筛选获得不同甘蓝耐裂球种质,为甘蓝耐裂球性研究和育种应用提供技术支撑和优异材料。     

中国14个特殊旁系族群的头面部特征比较

头面部特征是人类学各人种进行分类的重要依据,在人类学的研究中被用作亲缘关系的证据。2006-2016年在四川、云南、西藏、贵州、海南、新疆、内蒙古共调查14个族群成人2989人(男性1434人,女性1555人)的16项头面部指标,比较这些族群头面部特征差异。研究结果如下:1)在男性族群中木雅人、尔苏人、临高人、白马人的面宽、头宽均较大。图瓦人、布里亚特人、摩梭人的面宽、头宽、形态面高、鼻高值均较大。僜人、革家人、莽人的面宽、头宽较小,而形态面高、鼻高值较大。空格人的面宽、头宽、形态面高、鼻高值均较小。2)在女性族群中图瓦人、布里亚特人的头宽、面宽、鼻高、耳上头高均较大。革家人、空格人的头宽、面宽、鼻高、耳上头高均较小。木雅人、尔苏人、八甲人、白马人、夏尔巴人的头宽、面宽较大,鼻高、耳上头高较小。僜人、克木人、莽人的头宽、面宽较小,而鼻高、耳上头高较大。3)头宽、容貌耳长跟纬度、年平均气温、年降雨量等环境因子相关性较高。4)通过聚类分析和主成分分析木雅人、尔苏人、白马人与羌族头面部特征比较接近。克木人与佤族头面部特征最为接近。革家人、僜人、莽人头面部特征比较接近。图瓦人、布里亚特人头面部...     

Using an evolutionary algorithm to determine the parameters of a biologically inspired model of head direction cells

A biologically inspired model of head direction cells is presented and tested on a small mobile robot. Head direction cells (discovered in the brain of rats in 1984) encode the head orientation of their host irrespective of the host’s location in the environment. The head direction system thus acts as a biological compass (though not a magnetic one) for its host. Head direction cells are influenced in different ways by idiothetic (host-centred) and allothetic (not host-centred) cues. The model presented here uses the visual, vestibular and kinesthetic inputs that are simulated by robot sensors. Real robot-sensor data has been used in order to train the model’s artificial neural network connections. The main contribution of this paper lies in the use of an evolutionary algorithm in order to determine the values of parameters that determine the behaviour of the model. More importantly, the objective function of the evolutionary strategy used takes into consideration quantitative biological observations reported in the literature.     

Bumblebee Homing: The Fine Structure of Head Turning Movements

Changes in flight direction in flying insects are largely due to roll, yaw and pitch rotations of their body. Head orientation is stabilized for most of the time by counter rotation. Here, we use high-speed video to analyse head- and body-movements of the bumblebee Bombus terrestris while approaching and departing from a food source located between three landmarks in an indoor flight-arena. The flight paths consist of almost straight flight segments that are interspersed with rapid turns. These short and fast yaw turns (“saccades”) are usually accompanied by even faster head yaw turns that change gaze direction. Since a large part of image rotation is thereby reduced to brief instants of time, this behavioural pattern facilitates depth perception from visual motion parallax during the intersaccadic intervals. The detailed analysis of the fine structure of the bees’ head turning movements shows that the time course of single head saccades is very stereotypical. We find a consistent relationship between the duration, peak velocity and amplitude of saccadic head movements, which in its main characteristics resembles the so-called "saccadic main sequence" in humans. The fact that bumblebee head saccades are highly stereotyped as in humans, may hint at a common principle, where fast and precise motor control is used to reliably reduce the time during which the retinal images moves.     

Morphofunctional aspects of the head capsule topography in Aculeata (Hymenoptera)]

According to degree of segmental fusion insect head is the most integrated part of the body. Head skeleton subdivides into capsule and skeleton of appendages. Exo- and endoskeleton (tentorium) of head capsule have complex segmental origin. Marked margins are generally absent between such traditionally discriminated capsule parts as clypeus, frons, vertex, occiput, genae, etc. Relative position to marked structures (appendages, eyes, ocelli, occipital foramen and etc.) defines the capsule parts, but homologization of last ones is complicated both by absence of substantive functions and complex segmental origin. Based on the technological point of view author characterizes head capsule construction in Aculeata. Capsule parts were studied as components of six technological systems associated with the head: maxillolabial, antennal, pharyngeal, optical, cranio-articulate and mandibular. Spatial relations, named by I.I. Schmalhausen as topographical co-ordinations, integrate head systems. Therefore relative position of the capsule parts incorporated in such systems is unvaried under any reconstruction. At the same time varieties of their forms and proportions reflect on form and topography of capsule as a whole. Comparative analysis of the capsule construction in Bethyloidea, Formicoidea, Sphecoidea, Vespoidea, Pompiloidea and Scolioidea has shown that many differences are determined by mutual modification of technological systems. In particular the increase in head elevation related with reconstruction of cranio-articulate system is accompanied with the shift of antennae to anterior end of the head. The capsule construction in Aculeata considered to be represented by hypognathous, prognathous and hypo-prognathous morphological types that determine head orientation towards longitudinal body axis. The role of topographical co-ordinations in formation of prognathous or hypognathous condition of the head in Aculeata is discussed.     

Head Pilot: A new webcam-based Head Tracking System tested in permanently disabled patients

Persons with cerebral palsy (CP) need to modify their lifestyle in order to carry out daily activities. Assistive technology facilitates communication and improves the domestic environment and mobility. The STARNAV Company has developed a Head Tracking System, Head Pilot, which uses a robust algorithm that measures, in real-time, head motion from a webcam. Head Pilot aims to control any informatic and domotic interface controlling the pointer of a PC. This work aims to create an assistive technology that is easy to use once it is set up and used. The system offers an interface control, which allows individual users to adjust the system for their comfort. The system displays a toolbar allowing the patient to choose the velocity of the pointer and to choose from several different ways to validate a task. The objective of this study was to evaluate the performance of Head Pilot by using five computerized tests of validation. Seven participants with disabilities were compared to seven participants with no relevant medical history (control group). Two versions of the software were developed and displayed on a computer screen. The time to complete the tests were measured and compared to a control group. Before testing, the disabled persons had received an orthoptic assessment, a cognitive evaluation, and a cervical motor check. Head Pilot was validated for use by the majority of users with CP who were able to control a computer except for the subject with incomplete locked-in syndrome, who required an Eye Tracker System.     

Assessment of microsatellite instability in head and neck cancer using consensus markers

Head and neck cancer is the sixth most common cancer in the world and one of the most lethal cancers. Microsatellite instability is an important characteristic of tumor cells and is observed both in presence and absence of mismatch repair gene mutations. The importance of microsatellite instability in head and neck cancer is not well established due to the lack of a consensus panel and selection of different markers, criteria and methodological variances. The main objective of this study was to investigate the performance of a consensus panel of microsatellite repeats by automated fragment analysis. Matched tumor and normal tissue samples from 99 patients were analyzed using five mononucleotide markers. Following PCR the amplified fragments were analyzed by capillary electrophoresis on an ABI 310 genetic analyzer. Microsatellite instability was observed in 26 patients. In 17 patients instability was detected at multiple loci. NR21 and BAT25 were the most frequently altered targets. These two mononucleotide markers could detect all samples displaying high-instability. In this study we describe a standardized fluorescent multiplex PCR combined with computerized analysis, which allows rapid and accurate analysis of a high number of samples and obviates the need to compare tumors with matching normal tissue.     

Correlating head shape with ecological variables in rock-dwelling haplochromines (Teleostei: Cichlidae) from Lake Victoria

An exploratory analysis was made of the head shape of cichlid fishes. A 3-D head truss was used, which allowed approximations of the volumes of three compartments of the head. We applied the method to six species of rock-dwelling haplochromine cichlids, of which we studied 12 populations from four rocky islands in the southern part of Lake Victoria. Head shape was correlated with eight environmental variables. Truss distances and compartment volumes correlated with these variables, e.g. volumes of the compartments containing the gills correlated (negatively) with oxygen levels; truss distances, including the oral jaws and their musculature, correlated with food composition; and eye size correlated with width of the transmission spectrum. Another finding was the likely architectonic interactions between anatomical elements. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 39–48.     

Heads up: evolution of exaggerated head length in the minute litter bug genus <Emphasis Type="Italic">Nannocoris</Emphasis> Reuter (Hemiptera: Schizopteridae)

Evolutionary biologists have long been intrigued by exaggerated morphologies tied to sexual or natural selection. In insects, relatively few studies have investigated the evolution of such traits at the genus level and above and have used comparative phylogenetic methods to do so. We here investigate the interspecific evolution of head length in the minute litter bug genus Nannocoris Reuter based on the first phylogenetic hypothesis of the group (25 ingroup species, five gene regions, 3409 bp) and ancestral state reconstruction. Head lengths in this speciose genus range from approximately one sixth of the total body length to more than a quarter of the body length, while the head and mouthpart (rostrum) lengths are correlated. Different species therefore possess a markedly different reach of the rostrum when extended. The analyses show that head length evolution in Nannocoris is plastic, with head length elongations and reductions occurring in several clades, derived from ancestors with moderately elongated heads. Evidence is provided that exaggerated head lengths evolved through elongation of either the genal (pricei group) or the tip (arimensis group) region of the head. The biology of species in the genus Nannocoris is unknown, but given the lack of sexual dimorphism of head lengths, we speculate that head evolution in this genus may be driven by natural selection, potentially in the context of prey capture.