Sensory organs of the thoracic legs of the moth Manduca sexta

Summary The thoracic legs of the moth Manduca sexta acquire a new form and develop a new complement of sensory organs and muscles during metamorphosis from larva to adult. Because of our interest in the reorganization of neural circuitry and the acquisition of new behaviors during metamorphosis, we are characterizing sensory elements of larval and adult legs so that we may determine the contribution of new sensory inputs to the changes in behaviors. Here we describe the sensory structures of adult legs using scanning electron microscopy to view the external sensilla and cobalt staining to examine innervation by underlying sensory neurons. We find that, in contrast to larval legs, the adult legs are covered with a diverse array of sensilla. All three pairs of thoracic legs contain scattered, singly innervated scalelike sensilla. Campaniform sensilla occur singly or in clusters near joints. Hair plates, consisting of numerous singly innervated hairs, are also present near joints. Other more specialized sensilla occur on distal leg segments. These include singly innervated spines, two additional classes of singly innervated hairs, and three classes of multiply innervated sensilla. Internal sensory organs include chordotonal organs, subgenual organs, and multipolar joint receptors.     

THE FINE STRUCTURE OF COCKROACH CAMPANIFORM SENSILLA

Campaniform sensilla on cockroach legs provide a good model system for the study of mechanoreceptive sensory transduction. This paper describes the structure of campaniform sensilla on the cockroach tibia as revealed by light- and electron-microscopy. Campaniform sensilla are proprioceptive mechanoreceptors associated with the exoskeleton. The function of each sensillum centers around a single primary sense cell, a large bipolar neuron whose 40 µ-wide cell body is available for electrophysiological investigation with intracellular microelectrodes. Its axon travels to the central nervous system; its dendrite gives rise to a modified cilium which is associated with the cuticle. The tip of the 20 µ-long dendrite contains a basal body, from which arises a 9 + 0 connecting cilium. This cilium passes through a canal in the cuticle, and expands in diameter to become the sensory process, a membrane-limited bundle of 350–1000 parallel microtubules. The tip of the sensory process is firmly attached to a thin cap of exocuticle; mechanical depression of this cap, which probably occurs during walking movements, effectively stimulates the sensillum. The hypothesis is presented that the microtubules of the sensory process play an important role in mechanoelectric transduction in cockroach campaniform sensilla.     

External morphology and distribution of the antennal sensilla of the stonefly,Paragnetina media (Walker) (Plecoptera : Perlidae)

The distribution and external morphology of sensilla on the antennae of nymphal and adult stonefly, Paragnetina media (Plecoptera : Perlidae) were studied with light and scanning electron microscopy. A peculiar arrangement of 3 types of sensilla was observed on the antennae of the nymphs. Thick- and thin-walled sensilla basiconica and coniform sensillar complexes occur in a group, and 6 to 7 such groups are located around the distal margin on the segments in the mid-region of the flagellum. Campaniform sensilla are concentrated in a ring around a crown of thick- and thin-walled sensilla basiconica on the distal end of the pedicel. Two types of trichoid sensilla, long wavy, and stout straight, are present on the flagellum of the nymph. Adult stoneflies have an antennal surface profusely covered only with long and short trichoid sensilla; all other nymphal type sensilla are absent. The lack of nymphal type sensilla on their antennae may be related to the adult's brief, non-feeding terrestrial life.     

Mathematical shape optimization of hip prosthesis design

The long-term success of artificial-joint replacement depends partly on the chances for acrylic cement failure and interface disruption. These chances can be diminished by an optimal load-transfer mechanism, whereby stress concentrations are avoided. The present paper introduces a method for numerical shape optimization, whereby the finite element method is used iteratively to determine optimal prosthetic designs, which minimize interface stresses. The method is first applied in a simplified one-dimensional model of a cemented femoral stem fixation, using acrylic cement. The results show that 30-70% cement and interface stress reductions can be obtained in principle with an optimized design. Although the actual optimal shape is susceptible to the characteristics of the joint load, the stem length, stem modulus, cement modulus and bone properties, its general geometrical characteristics are consistent, featuring proximal and distal tapers, and a belly-shaped middle region. These general characteristics are confirmed in a more realistic two-dimensional FEM model. It is concluded that this method of shape optimization can provide a meaningful basis for prosthetic design and analysis activities in general.     

Finite elements/Taguchi method based procedure for the identification of the geometrical parameters significantly affecting the biomechanical behavior of a lumbar disc

The aim of this work is to show a quick and simple procedure able to identify the geometrical parameters of the intervertebral disc that strongly affect the behavior of the FEM model. First, we allocated a selection criterion for the minimum number of geometrical parameters that describe, with a good degree of approximation, a healthy human vertebra. Next, we carried out a sensitivity analysis using the ‘Taguchi orthogonal array’ to arrive at a quick identification of the parameters that strongly affect the behavior of the Fem model.     

中华蚊蝎蛉成虫口器感器的超微结构

口器感器在昆虫取食活动中起着重要作用, 但蚊蝎蛉成虫口器上感器的种类和形态迄今未见报道。我们利用扫描电子显微镜, 观察了中华蚊蝎蛉Bittacus sinensis Walker成虫口器上的感器。结果显示: 中华蚊蝎蛉口器上共有8种感器, 分别为锥形、毛形、刺形、指形、掌状、钟形、柱状感器及Böhm氏鬃毛, 主要集中于内唇、 下颚须以及下唇须上。锥形感器和刺形感器数量最多; 毛形感器主要在下颚轴节、 茎节和下唇的亚颏和前颏有分布; 钟形感器和Böhm氏鬃毛只存在于下唇须和下颚须上。下颚须端节和下唇须端节的感器种类相同, 以锥形感器为主。高度骨化的上颚以及下颚内颚叶与外颚叶上未发现感器分布。简要讨论了口器感器在昆虫分类中的意义。     

The fine structure of haltere sensilla in the blowfly Calliphora erythrocephala (Meig.), with scanning electron microscopic observations on the haltere surface

The dipteran haltere incorporates large numbers of regularly disposed mechanoreceptors providing the sensory input enabling the vibrating haltere to function as a gyroscopic organ of equilibrium. Campaniform sensilla of the basal and scapal regions have been investigated by light and transmission electron microscopy, and these observations are augmented by scanning electron studies of the cuticle overlying the groups of sensilla. Each sensillum possesses a specialized fan-shaped terminal containing a complex and ordered association of microtubules and filaments. The transmission of stress to this region via the cuticle, and its possible role in transduction is considered. The fine structure of apical and basal sections of the distal sensory process and associated sheath cells is described; the functional significance of the distribution of mitochondria and other components is discussed. The organization of haltere chordotonal sensilla is described briefly, and compared with other mechanoreceptors with particular reference to microtubules and scolopale structures.     

Sensilla of the antennae and the labial and maxillary palps of Blattella germanica (L.) (Dictyoptera: Blattellidae): Their classification and distribution

The various sensilla on the antennae and on the labial and maxillary palps of Blattella germanica (L.) were studied. Thick-walled chemoreceptors with fluted shafts and articulated bases are located on the antennae and on the labial and maxillary palps. Thin-walled chemoreceptors, without fluted shafts or articulated bases, are restricted to the flagellar segments of the antennae and to the distal segments of the palps. Antennae of adult males have more thin-walled chemoreceptors than do those of females. Hair-plate sensilla are found at the scape-head and scape-pedicel joints, and at the joints of segments on the palps. Campaniform sensilla are concentrated as a ring around the distal margin of the pedicel, and are also scattered singly on the scape, pedicel, and flagellar segments of the antennae, and on the first segment of the maxillary palps. Occasionally, a few sensilla coeloconica and cold receptor sensilla are found on the antennal flagellum.     

Sensilla of the larvae of Delia radicum L., D. Floralis F. and D. Antiqua MG. (diptera : Anthomyiidae)

A comparative SEM study of the sensilla of larval Delia radicum, D. floralis and D. antiqua (Diptera : Anthomyiidae) was undertaken. All had a dorsal organ and an anterior organ. These may contain olfactory receptors, contact chemo- and mechanoreceptors. Delia radicum and D. floralis also possessed a ventral organ, which is a possible chemo- and mechanoreceptor. Campaniform (mechanoreceptor) and hair sensilla, which may be humidity receptors, were present on the body segments.     

The distribution of and interactions between GABA-immunoreactive and non-immunoreactive processes presynaptic to afferents from campaniform sensilla on the trochanter of the locust leg

Summary Campaniform sensilla on the trochanter of the mesothoracic legs of the locust were backfilled with cobalt salts or horseradish peroxidase for light and electron microscopy. The distribution of the terminal branches of afferent neurones in the thoracic ganglia were described from wholemount preparations and from thick slices through the ganglia. Ultrathin sections of identified branches were processed with GABA antibodies using a post-embedding immunogold technique and examined in the electron microscope. Input synapses were observed on fine varicose branches in all regions of the terminal arborisations close to the sites of afferent output. The major branches neither make nor receive synapses. Seventy-two percent of the input synapses are made by processes immunoreactive for GABA. Immunoreactive and non-immunoreactive processes synapse onto afferent terminals in close proximity. In some instances GABA-immunoreactive processes presynaptic to an afferent are also presynaptic to a non-immunoreactive presynaptic processes strongly suggesting that different presynaptic influences can interact directly with each other.     

Studying the deformation of arachnid slit sensilla by a fracture mechanical approach

Slit sensilla are sensory organs which measure strains in the exoskeleton of arachnids. They occur as isolated slits, in loose groups and in close parallel arrangements known as lyriform organs or compound slit sensilla. The deformations of the slits' faces induced by far-field strains acting on groups of slits are studied using Kachanov's analytical approximations for the opening displacements of cracks, a method developed within the framework of fracture mechanics. The accuracy of the approach is assessed by comparisons with results obtained by finite element analysis. The limits of its applicability to slit sensilla are found to be reached when the lateral spacing between interacting slits is less than half their length, i.e., the method is suitable for studying single slits and loose groups but not lyriform organs. The influence of a number of geometrical parameters of slit sensilla on the deformation patterns of the faces of parallel slits in generic arrangements is studied, viz., spacing between slits, longitudinal shifts between slits, and slit length. The results are presented as opening distances along the length of the cracks and in terms of normalized diagrams that relate the opening distances at mid-length of the slits to the geometrical parameters. In addition, Kachanov's method is used to find a set of slit lengths that give rise to prescribed opening distances.     

Central projections of campaniform sensilla on the cerci of crickets and cockroaches

Summary Campaniform sensilla associated with filiform hairs comprise an important receptor type of the multimodal sensory system of the cerci of crickets and cockroaches. Their axon projections were investigated using iontophoretic cobalt injection into single sensilla.In crickets (Gryllus bimaculatus, Acheta domestica), six different types of cereal campaniform sensilla projections can be distinguished on the basis of their axonal arborizations and terminations. Typically, a proportion of cereal campaniform sensilla, associated with long filiform hairs, give rise to axons that ascend as through fibres from the terminal ganglion to reach the sixth abdominal ganglion. Cereal campaniform sensilla associated with clavate hairs have projections restricted to the terminal ganglion alone.Whereas in crickets axons of cercal campaniform sensilla invade only certain segmental neuropils in the terminal ganglion, in cockroaches (Periplaneta americana) axons from cercal campaniform sensilla branch in every segmental neuropil. A proportion of cereal campaniform sensilla in this species also gives rise to through fibres to the fifth abdominal ganglion.We discuss morphological and functional interpretations of differences between crickets and cockroaches and consider the significance of this type of receptor in the context of previous studies of the cercal system.     

Extracellular crystalline material in intercellular spaces of cockroach peripheral glia

Campaniform sensilla on legs of the cockroach, Blaberus discoidalis, are mechanoreceptors; each sensifum functions via a single bipolar neuron. The cell bodies of the bipolar neurons are tunicated; that is, they are spirally wrapped by one or more glial cells. An elaborate extracellular channel is defined by the plasma membranes of adjacent glial cell folds surrounding a given neuron. The electron microscope reveals that this extracellular space often contains conspicuous crystalline material whose lattice planes, oriented at right angles to the long crystal axis, are manifest as parallel electron-dense lines separated by an intercentre distance of 150 A. The chemical nature of these crystals has not been determined in the present study. Like most biological crystals, however, this precisely ordered crystalline material is probably proteinaceous.     

Enhanced Specificity of TPMT*2 Genotyping Using Unidirectional Wild-Type and Mutant Allele-Specific Scorpion Primers in a Single Tube

Genotyping of thiopurine S-methyltransferase (TPMT) is recommended for predicting the adverse drug response of thiopurines. In the current study, a novel version of allele-specific PCR (AS-PCR), termed competitive real-time fluorescent AS-PCR (CRAS-PCR) was developed to analyze the TPMT*2 genotype in ethnic Chinese. This technique simultaneously uses wild-type and mutant allele-specific scorpion primers in a single reaction. To determine the optimal conditions for both traditional AS-PCR and CRAS-PCR, we used the Taguchi method, an engineering optimization process that balances the concentrations of all components using an orthogonal array rather than a factorial array. Instead of running up to 264 experiments with the conventional factorial method, the Taguchi method achieved the same optimization using only 16 experiments. The optimized CRAS-PCR system completely avoided non-specific amplification occurring in traditional AS-PCR and could be performed at much more relaxed reaction conditions at 1% sensitivity, similar to traditional AS-PCR. TPMT*2 genotyping of 240 clinical samples was consistent with published data. In conclusion, CRAS-PCR is a novel and robust genotyping method, and the Taguchi method is an effective tool for the optimization of molecular analysis techniques.     

An accessory olfactory pathway in Lepidoptera: the labial pit organ and its central projections in Manduca sexta and certain other sphinx moths and silk moths

Summary In the hawkmoth, Manduca sexta, the third segment of each labial palp contains a pit, which houses a densely packed array of sensilla. We have named this structure the labial pit organ (LPO). The sensilla within the pit are typical of olfactory receptors, characterized by a grooved surface, wall pores, and pore tubules. Axons arising from receptor cells that innervate these sensilla project bilaterally to a single glomerulus in each antennal lobe. We have compared this central projection with that in three other species of Manduca (M. quinquemaculata, M. dilucida, and M. lanuginosa) and in the silkmoths Antheraea polyphemus and Bombyx mori. A bilateral projection to a single glomerulus in each antennal lobe is present in all cases. We suggest that the LPO serves as an accessory olfactory organ in adult Lepidoptera.     

A new numerical approach to mechanically analyse biological structures

In this work, an advanced discretization meshless technique is used to study the structural response of a human brain due to an impact load. The 2D and 3D brain geometrical models, and surrounding structures, were obtained through the processing of medical images, allowing to achieve a realistic geometry for the virtual model and to define the distribution of the mechanical properties accordingly with the medical images colour scale. Additionally, a set of essential and natural boundary conditions were assumed in order to reproduce a sudden impact force applied to the cranium. Then, a structural numerical analysis was performed using the Natural Neighbour Radial Point Interpolation Method (NNRPIM). The obtained results were compared with the finite element method (FEM) and a solution available in the literature. This work shows that the NNRPIM is a robust and accurate numerical technique, capable to produce results very close to other numerical approaches. In addition, the variable fields obtained with the meshless method are much smoother than the FEM corresponding solution.     

Protein structure prediction in a 210-type lattice model: parameter optimization in the genetic algorithm using orthogonal array

We have applied the orthogonal array method to optimize the parameters in the genetic algorithm of the protein folding problem. Our study employed a 210-type lattice model to describe proteins, where the orientation of a residue relative to its neighboring residue is described by two angles. The statistical analysis and graphic representation show that the two angles characterize protein conformations effectively. Our energy function includes a repulsive energy, an energy for the secondary structure preference, and a pairwise contact potential. We used orthogonal array to optimize the parameters of the population, mating factor, mutation factor, and selection factor in the genetic algorithm. By designing an orthogonal set of trials with representative combinations of these parameters, we efficiently determined the optimal set of parameters through a hierarchical search. The optimal parameters were obtained from the protein crambin and applied to the structure prediction of cytochrome B562. The results indicate that the genetic algorithm with the optimal parameters reduces the computing time to reach a converged energy compared to nonoptimal parameters. It also has less chance to be trapped in a local energy minimum, and predicts a protein structure which is closer to the experimental one. Our method may also be applicable to many other optimization problems in computational biology.     

六斑月瓢虫触角及感觉器扫描电镜观察

[目的] 明确六斑月瓢虫雌雄成虫触角感觉器种类、分布及形态特征。[方法] 利用扫描电子显微镜对六斑月瓢虫雌、雄成虫触角形态及触角感受器超微结构进行观察。[结果] 六斑月瓢虫成虫触角由柄节、梗节和鞭节组成,柄节长度与宽度显著大于梗节长度与宽度;鞭节分为9个亚节,末端3节横向膨大呈锤状。雌雄成虫触角上共有8种感觉器:刺形感觉器(SC)、毛形感觉器(ST)、锥形感觉器(SB)、腔形感觉器(CaS)、钟形感觉器(CS)、哑铃形感觉器(DS)、香肠形感觉器(SS)及B?hm氏鬃毛感觉器(BB)。以毛形感觉器和刺形感觉器分布最广,遍布触角;B?hm氏鬃毛仅存在于触角柄节与梗节;触角鞭节第9亚节顶端密布7种触角感觉器。六斑月瓢虫雌雄成虫触角长度、触角感觉器类型及分布无显著差异。[结论] 六斑月瓢虫成虫触角上共有8种感觉器,其触角可能具有感知机械刺激、识别化学信息素及感受温湿度变化的作用。本研究为进一步了解六斑月瓢虫触角与其行为间的关系提供基础资料。     

The construction of a simultaneous functional order in nervous systems

The functional order of a collection of nervous elements is available to the system itself, as opposed to the anatomical geometrical order which exists only for external observers. It has been shown before (Part I) that covariances or coincidences in the signal activity of a neural net can be used in the construction of a simultaneous functional order in which a modality is represented as a concatenation of districts with a lattice structure. In this paper we will show how the resulting functional order in a nervous net can be related to the geometry of the underlying detector array. In particular, we will present an algorithm to construct an abstract geometrical complex from this functional order. The algebraic structure of this complex reflects the topological and geometrical structure of the underlying detector array. We will show how the activated subcomplexes of a complex can be related to segments of the detector array that are activated by the projection of a stimulus pattern. The homology of an abstract complex (and therefore of all of its subcomplexes) can be obtained from simple combinatorial operations on its coincidence scheme. Thus, both the geometry of a detector array and the topology of projections of stimulus patterns may have an objective existence for the neural system itself.