Corrosion casts as a method for investigation of the insect tracheal system

Summary The tracheal systems of five insect species (two species of ants, worker bee, housefly and the cabbage butterfly) have been studied by scanning electron microscopy of corrosion casts. This technique, which is commonly used for the investigation of vertebrate vasculature, is adapted to demonstrate the ultrastructure of the insect respiratory organ. The problem of filling a blind ending system was solved by injecting the resin Mercox into the evacuated tracheae through a thoracal spiracle. After polymerization of the resin, the tissue was digested enzymatically and chemically. The three-dimensional structure of the tracheal system was investigated by scanning electron microscopy. The technique used here displays for the first time the complex morphology of the entire tracheal system in fine detail, especially the structure of spiracles, airsacs, tracheae and tracheoles. Smooth-walled terminal tracheoles show up in flight muscles. The finest tracheoles that could be identified have diameters of approximately 70 nm. This approaches the finest tracheoles portrayed by transmission electron micrographs.     

The development of the plasma membrane reticular system in the fat body of an insect

Several insect tissues have plasma membranes that are folded inwards to make a subsurface reticulum on faces that are exposed to hemolymph. The infolds have been called plasma membrane reticular systems (RSs) to distinguish them from the somewhat similar structures found in transporting epithelia. They are characterized by having negative charges on the plasma membranes of the entranceways and by the concentration of some hemolymph proteins in their lymph spaces. Their formation and loss in the fat body has been studied by scanning electron microscopy during the fifth stadium of Calpodes ethlius (Lepidoptera, Hesperiidae). Fat body cells begin the fifth stadium arranged in ribbons with the cells linked together by a fringe of processes. In the first stage many more processes form. These partially fuse together in the second stage, leaving a subsurface reticulum connected by narrow entrances to the lateral cell faces and the face below the basal lamina. Both the cell processes and the reticular systems that they enclose are usually axially orientated. The completed RS persists for the second half of the intermoult devoted to larval syntheses when the concentration of hemolymph proteins rises. After protein sequestration prior to pupation the RS is lost and the fat body returns to being a tissue of rounded cells linked by a few enmeshed processes.     

Mechanical properties of the tracheal mucosal membrane in the rabbit. II. Morphometric analysis.

Folding of the airway mucosal membrane provides a mechanical load that impedes airway smooth muscle contraction. Mechanical testing of rabbit tracheal mucosal membrane showed that the membrane is stiffer in the longitudinal than in the circumferential direction of the airway. To explain this difference in the mechanical properties, we studied the morphological structure of the rabbit tracheal mucosal membrane in both longitudinal and circumferential directions. The collagen fibers were found to form a random meshwork, which would not account for differences in stiffness in the longitudinal and circumferential directions. The volume fraction of the elastic fibers was measured using a point-counting technique. The orientation of the elastic fibers in the tissue samples was measured using a new method based on simple geometry and probability. The results showed that the volume fraction of the elastic fibers in the rabbit tracheal mucosal membrane was approximately 5% and that the elastic fibers were mainly oriented in the longitudinal direction. Age had no statistically significant effect on either the volume fraction or the orientation of the elastic fibers. Linear correlations were found between the steady-state stiffness and the quantity of the elastic fibers oriented in the direction of testing.     

The vacuolar-type ATPase from insect plasma membrane: immunocytochemical localization in insect sensilla

Summary This comparative immunocytochemical investigation provides evidence that the electrogenic potassium pump of insect sensilla is a vacuolar-type proton ATPase energizing potassium-proton antiport, as was shown recently for the electrogenic potassium pump in the larval midgut of the sphinx moth Manduca sexta. Antennal sensilla of the saturniid moth Antheraea pernyi were probed with antibodies to the midgut vacuolar-type ATPase. The monoclonal antibodies recognized their epitopes in the native and SDS-denatured state, and bound specifically to the subunit with the relative molecular mass (M_r) of 67000 (antibody 86-3) or to the subunits of M_r 28000 and 16000 (antibody 47-5). Both antibodies labelled the apical region of the auxiliary cells, as was demonstrated by immunofluorescence microscopy. Immunogold-electron microscopy localized the binding sites of the 47-5 antibody in the highly folded apical plasma membranes of the auxiliary cells. Labelling was selective and was detected in all types of examined sensilla (S. trichodea, S. styloconica, S. coeloconica). These findings are in agreement with the current view that an electrogenic potassium pump is situated in the apical plasma membrane of the auxiliary cells and that the pump is involved in driving the receptor current. They support the hypothesis that a proton-motive force generated by a vacuolar-type ATPase provides an alternative to the classical Na⁺/K⁺-ATPase to energize animal plasma membranes.     

Association of tracheal placodes with leg primordia in Drosophila and implications for the origin of insect tracheal systems

Adaptation to diverse habitats has prompted the development of distinct organs in different animals to better exploit their living conditions. This is the case for the respiratory organs of arthropods, ranging from tracheae in terrestrial insects to gills in aquatic crustaceans. Although Drosophila tracheal development has been studied extensively, the origin of the tracheal system has been a long-standing mystery. Here, we show that tracheal placodes and leg primordia arise from a common pool of cells in Drosophila, with differences in their fate controlled by the activation state of the wingless signalling pathway. We have also been able to elucidate early events that trigger leg specification and to show that cryptic appendage primordia are associated with the tracheal placodes even in abdominal segments. The association between tracheal and appendage primordia in Drosophila is reminiscent of the association between gills and appendages in crustaceans. This similarity is strengthened by the finding that homologues of tracheal inducer genes are specifically expressed in the gills of crustaceans. We conclude that crustacean gills and insect tracheae share a number of features that raise the possibility of an evolutionary relationship between these structures. We propose an evolutionary scenario that accommodates the available data.     

The fusogenic properties of the cytotoxins of cobra venom in a model membrane system

By the methods of EPR spinal probes, energy migration of triplet excitation and NMR spectroscopy, the structural changes on hydrocarbon region of membranes, the changes in dynamic state of water of lipid hydrate jacket, the intermembrane lipid material exchange and fusion of membranes induced by cytotoxins of cobra venom have been studied. The sequence of events preceded the membrane fusion is suggested. The probability of membrane fusion has been shown not to be determined by fusogenic agent structure only, but much it depends on lipid composition of membranes.     

The origin and functions of the insect peritrophic membrane and peritrophic gel

There is a a fluid (peritrophic gel) or membranous (peritrophic membrane, PM) film surrounding the food bolus in most insects. The PM is composed of chitin and proteins, of which peritrophins are the most important. It is proposed here that, during evolution, midgut cells initially synthesized chitin and peritrophins derived from mucins by acquiring chitin-binding domains, thus permitting the formation of PM. Since PM compartmentalizes the midgut, new physiological roles were added to those of the ancestral mucus (protection against abrasion and microorganism invasion). These new roles are reviewed in the light of data on PM permeability and on enzyme compartmentalization, fluid fluxes, and ultrastructure of the midgut. The importance of the new roles in relation to those of protection is evaluated from data obtained with insects having disrupted PM. Finally, there is growing evidence suggesting that a peritrophic gel occurs when a highly permeable peritrophic structure is necessary or when chitin-binding molecules or chitinase are present in food.     

The formation of the ecdysial droplets and the ecdysial membrane in an insect

Insect cuticle forms as a result of overlapping sequences of two kinds of process, those involving vesicles of the Golgi complex, and those related to transport through and/or assembly at the apical plasma membrane. The ecdysial droplets are the last layer of old cuticle to be deposited before ecdysis and form from the contents of secretory vesicles from Golgi complexes. Ecdysial droplets and secretory vesicles both stain with PTA and react with silver hexamine after oxidation with periodic acid. The vesicles discharge in localized apical areas devoid of microvilli where they accumulate as droplets measuring about 3 [ x 1 [. The. droplets span the last few lamellae of the endocuticle which becomes the ecdysial membrane. They dissolve to leave the ecdysial membrane full of holes at the time that the rest of the old cuticle is digested.     

Influence of the reciprocating movement on the performance of a membrane aeration system in insect cell cultures

Summary The influence of the reciprocating movement of a silicon membrane tubing aeration system on the metabolic performance of Spodoptera frugiperda cells was investigated in a stirred reactor.     

The formation of plasma membrane reticular systems in the oenocytes of an insect

Plasma membrane reticular systems (RSs) are infolds of the plasma membrane found in cells of several insect tissues that are not transporting epithelia. They form a subsurface reticular lymph space that may be involved in the loading and unloading of hemolymph carrier molecules. The development of a new RS during the fifth larval stadium has been studied in the oenocytes of Calpodes ethlius by scanning electron microscopy. The RS forms by the extension and progressive apical fusion of cell processes leaving a reticular lymph space below. Reticular system formation occurs in a front moving over the cell surface. The RS made in the 4th stadium persists through the moult to the 5th stage but diminishes for the next 3 days. A new intermoult RS then forms very quickly. Its time of formation follows the commitment ecdysteroid peak rather than the beginning of secretion by the wax glands. This new 5th stage RS is maintained during the period of intermoult synthesis, after which it declines and is nearly absent by the time of pupation.     

Beyond aerodynamics: The critical roles of the circulatory and tracheal systems in maintaining insect wing functionality

Insect wings consist almost entirely of lifeless cuticle; yet their veins host a complex multimodal sensory apparatus and other tissues that require a continuous supply of water, nutrients and oxygen. This review provides a survey of the various living components in insect wings, as well as the specific contribution of the circulatory and tracheal systems to provide all essential substances. In most insects, hemolymph circulates through the veinal network in a loop flow caused by the contraction of accessory pulsatile organs in the thorax. In other insects, hemolymph oscillates into and out of the wings due to the complex interaction of several factors, such as heartbeat reversal, intermittent pumping of the accessory pulsatile organs in the thorax, and the elasticity of the wall of a special type of tracheae. A practically unexplored subject is the need for continuous hydration of the wing cuticle to retain its flexibility and toughness, including the associated problem of water loss due to evaporation. Also, widely neglected is the influence of the hemolymph mass and the circulating flow in the veins on the aerodynamic properties of insect wings during flight. Ventilation of the extraordinarily long wing tracheae is probably accomplished by intricate interactions with the circulatory system, and by the exchange of oxygen via cutaneous respiration.     

昆虫抗冻蛋白的分离纯化及特性分析

昆虫抗冻蛋白具有很高的热滞活性,可保护机体免受结冰引起的伤害。昆虫抗冻蛋白的分离纯化多采用凝胶过滤层析、离子交换层析及HPLC等技术,已用于鱼类抗冻蛋白纯化的冰亲和纯化(IAP)技术也可考虑应用于昆虫抗冻蛋白的分离提纯。昆虫抗冻蛋白具有高活性,规则的一级结构及类似的冰晶结合表面等特性。     

New field of insect science: Research on the use of insect properties

In recent years, research on “insect properties” has been attracting much attention for industrial applications of insect technology. This is a new field of research that attempts to analyze specific physiological properties of insects to develop technology for helping humankind. The term “insect properties” has been used to refer to “specific biological functions of insects” since around 1986, and it is now widely accepted in Japan. From 1996, the National Institute of Sericultural and Entomological Science (NISES) promoted “Research for utilization of insect properties” as a “Center of Excellence (COE)” project funded by the Science and Technology Agency. At this point, a new research field called “Research for utilization of insect properties” was initiated, and this led to the recognition of this field by the academic community. In the 21st century, remarkable results, including the development of transgenic silkworms and the full decoding of the silkworm genome, have been achieved. It is expected that this advanced technology will be a powerful tool for progress of research on the use of insect properties. This review presents an overview of the current state of research on use of insect properties as a new technology.     

Dielectric properties of insect tissues

In order to explain some effects of microwave irradiation on insects it is necessary to consider a mathematical model. The knowledge of dielectric properties of a typical insect tissue is crucial for such a model. A method based on shift of resonant frequency and of quality factor measurement in a resonator both before and after the insertion of samples was used. The method (measurements at a frequency of 2375 MHz) has been described in detail. A large number of measurements were performed on different kinds of typical insect tissues (cuticle, fat body, muscles, reproductive organs and eggs) for their dielectric properties. The values obtained compare well to those reported in the literature for some mammals. Differences seemed to depend on different water-to-fat content ratios. However, no simple dependence on the water content was found. Values obtained from insect tissue material have been discussed in detail.