Types Of Cuticle Research Articles

Cuticle-catalyzed coupling between N-acetylhistidine and N-acetyldopamine

Several types of insect cuticle contain enzymes catalyzing the formation ofof adducts between N-acetyldopamine (NADA) and N-acetylhistidine (NAH). Two such adducts, NAH-NADA-I and NAH NADA-II, have been isolated and their structures determined. In one of the adducts the link connecting the two residues occurs between the I-position (ß-position) in the NADA side chain and the 1-N atom (τ-N) in the imidazole ring of histidine. Diphenoloxidase activity alone is not sufficient for formation of this adduct, whereas extracts containing both diphenoloxidase and o-quinone- p-quinone methide isomerase activities catalyze the coupling reaction. The adduct consists of a mixture of two diastereomers and they are presumably formed by spontaneous reaction between enzymatically produced NADA- p-quinone methide and N-acetylhistidine. The other adduct has been identified as a ring addition product of N-acetylhistidine and NADA. In contrast to the former adduct it can be formed by incubation of the two substrates with mushroom tyrosinase alone. An adduct between N-acetylhistidine and the benzodioxan-type NADA-dimer is produced in vitro, when the N-acetylhistidine-NADA adduct is incubated with NADA and locust cuticle containing a 1,2-dehydro-NADA generating enzyme system. Trimeric NADA-polymerization products of the substituted benzodioxan-type have been obtained from in vivo sclerotized locust cuticle, confirming the ability of cuticle to produce NADA-oligomers. The results indicate that some insect cuticles contain enzymes promoting linkage of oxidized NADA to histidine residues. It is suggested that histidine residues in the cuticular proteins can serve as acceptors for oxidized NADA and that further addition of NADA-residues to the phenolic groups of bound NADA can occur, resulting in formation of protein-linked NADA-oligomers. The coupling reactions identified may be an important step in natural cuticular sclerotization.

A new procedure for handling impervious biological specimens.

A new application of techniques for preparing impervious biological specimens for light microscopy (LM) and transmission electron microscopy (TEM) has been developed. Microwave irradiation was used to facilitate fixation. A priming technique was used to increase the bonding of the outer surface of the specimens with the resin. Priming the waxy or cuticular surface with Z-6040 (gamma-glycidoxypropyl trimethoxysilane) solved the problem of specimen "pull out" from the resin. Insect specimens with various types of cuticles (waxy or chitinous) and seeds were successfully studied ultrastructurally using this technique.

Enzymatic activities involved in incorporation of N-acetyldopamine into insect cuticle during sclerotization

During sclerotization of insect cuticle, N-acetyldopamine (NADA) is enzymatically oxidized before reaction with cuticular proteins. Not all oxidized NADA reacts with cuticular structural materials, a small fraction reacts with water or other available low molecular weight compounds to give soluble products. Various types of cuticle were incubated with excess NADA and the products studied by reversed phase high performance liquid chromatography (RP-HPLC) to obtain information on the enzymatic activities in the cuticle. The occurrence of at least two enzymes competing for NADA and present in different proportions in the various types of cuticle can explain the results. NADA may be incorporated into cuticle via α,β-dehydro-NADA (β-sclerotization) or via quinone methides and o-quinones, and the actual course of sclerotization will depend upon the relative activities of the enzymes involved. The various pathways may all be used simultaneously.

Oxidation of N- β-alanyldopamine by insect cuticles and its role in cuticular sclerotization

The oxidation products formed when various types of insect cuticle were incubated with N- β-alanyldopamine (NBAD) have been studied by means of reversed phase high performance liquid chromatography, and compared to the corresponding products obtained when N-acetyldopamine (NADA) was incubated with the cuticles. The results indicate that NBAD is oxidized to o-quinone and quinone methide derivatives. In contrast, NADA can be oxidized by some cuticles not only to o-quinone and quinone methide derivatives, but it can also be desaturated to α, β-dehydro- N-acetyldopamine, a probable intermediate in β-sclerotization. Some implications for in vivo sclerotization are discussed.

Cuticular proteins: The neglected component

AbstractThis paper emphasizes the importance of the protein component of cuticles. Correlation of electrophoretic charge distribution of individual cuticular proteins and physical properties of the cuticles from which they were extracted, as well as interpopulation and interspecies conservation of electrophoretic patterns, are used to argue that individual proteins play precise roles in the cuticle. Glycosylation of cuticular proteins is described, but no function for these modifications is yet known. Analogy is drawn to analyses of chorion proteins and the case is made that analysis of amino acid sequence data is likely to provide insights into how cuticular proteins and chitin interact to construct the diverse types of cuticles.

Mechanical properties of mineralized and sclerotized puparial cuticles of the flies Musca autumnalis and M. domestica

AbstractMechanical properties of mineralized and sclerotized puparial cuticles of the face fly, Musca autumnalis, and the house fly, M. domestica, respectively, were determined. The thickness of mineralized cuticle is 55% greater than that of sclerotized cuticle (thickness = 41.7 and 26.8 μm, respectively) from puparia of similar diameter (2.4 to 2.8 mm). Nonetheless, breaking forces for both types of puparial cuticle are similar (load ultimate strength = 9.3–10.9 g). However, the mineralized puparia are considerably stiffer than sclerotized puparia (elastic modulus = 346.4 kg mm−1 and 711.5 kg mm−1, respectively) and exhibit fracture at relatively lower load values (percentage total deformation at fracture = 3.5% and 11.0%, respectively). Differences in mechanical properties of puparial cuticle are probably due to the kinds and quantities of cuticular components: The mineralized puparia contain appreciably more inorganic components such as calcium, phosphorus and magnesium, while the sclerotized puparia consist of relatively more organic components such as proteins and phenolics. The evolutionary and functional significance of mineralization and sclerotization as mechanisms for puparial cuticle stabilization is discussed.

The transfer of lipid in insects from the epidermal cells to the cuticle

The structure of the pore canals and the tubular filaments they contain are described in a series of insects and types of cuticle. In all these cuticles the tubular filaments arise from the plasma membrane of the epidermal cells and they contain argentaffin material, regarded as sclerotin precursors, and lipid-staining material, regarded as wax precursors. These materials are transferred to the inner epicuticle and are exuded over the surface of the outer epicuticle to form the waterproofing layer as described in the preceding paper. They are also transported to those parts of the endocuticle destined to form hard exocuticle. There are no terminations of tubular filaments in the soft cuticle of Manduca larva, in the soft expanding cuticle of Rhodnius, and in the non-sclerotized post-ecdysial endocuticle of Tenebrio, Apis, etc. In the puparium of Calliphora lipid appears to be added by the epidermal cells directly and not by way of tubular filaments. It is confirmed that lipid is a component of sclerotized cuticle.

Evidence that pupal and adult cuticular proteins are coded by different genes in the silkmoth Antheraea polyphemus

The poly A + mRNAs present in the wing epidermis of the silkmoth Antheraea polyphemus during the period of synthesis of juvenile hormone-induced second pupal cuticle and adult cuticle were analysed by cDNA-mRNA hybridizations. The hybridization data indicate 60% similarity and 40% differences. The cDNAs unique to each type of cuticle (null cDNAs) were isolated and were shown to belong to the moderately abundant class. The number of mRNAs unique to each stage is calculated to be about 400. Analysis of the total mRNAs by translation in in vitro cell free systems indicate the presence of mRNAs unique to each type of cuticle which yield products with different isoelectric points and molecular weights. Similar differences were observed by comparing the cuticular polypeptides in the two kinds of cuticle using two dimensional electrophoresis. The results from the three different approaches provide evidence which supports the hypothesis that the pupal and adult cuticular proteins are coded by different messages and hence probably different genes.

Overlapping stage-specific sets of numerous small collagenous polypeptides are translated in vitro from Caenorhabditis elegans RNA

Caenorhabditis elegans synthesizes four morphologically distinct types of collagenous cuticles during its lifetime. We show that in RNA populations isolated early or late during the L4-to-adult molt, chick and nematode collagen DNAs hybridize strongly to RNAs of about 1.2 kb. Different but over-lapping classes of correspondingly small collagenous polypeptides (310–460 residues in length) are translated in vitro from these two populations and from RNA isolated at the L2-to-dauer molt. Over 60 different collagenous translation products are identified. These collagenous polypeptides are smaller than mature cuticle collagens and smaller than most vertebrate collagens. They probably represent cuticle collagen precursors and the primary products of the cuticle collagen genes of C. elegans.

Cuticular Anatomy of Angiosperm Leaves from the Lower Cretaceous Potomac Group. I. Zone I Leaves

Angiosperm leaf cuticles from the oldest part of the Potomac Group reinforce previous paleobotanical evidence for a Cretaceous flowering plant diversification. Dated palynologically as Zone I of Brenner (Aptian?), these remains show a low structural diversity compared to later Potomac Group and modern angiosperms. All cuticle types conform to a single plan of stomatal construction that is unusual in its extraordinary plasticity: both the number of subsidiary cells and their arrangement vary greatly on a single epidermis, such that the stomata might be classified as paracytic, anomocytic, laterocytic, and intermediate. Such stomatal diversity is uncommon in extant angiosperms but is known from a few Magnoliidae. Many species possess secretory cells comparable to the oil cells of modern Magnoliidae, and a few show the bases of probable uniseriate hairs. None of the cuticle types can be assigned to a single modern family, but several show similarities with Chloranthaceae and Illiciales. These results support the concept that subclass Magnoliidae includes some of the most primitive living angiosperms.

CUTICULAR ANATOMY OF ANGIOSPERM LEAVES FROM THE LOWER CRETACEOUS POTOMAC GROUP. I. ZONE I LEAVES

Angiosperm leaf cuticles from the oldest part of the Potomac Group reinforce previous paleobotanical evidence for a Cretaceous flowering plant diversification. Dated palynologically as Zone I of Brenner (Aptian?), these remains show a low structural diversity compared to later Potomac Group and modern angiosperms. All cuticle types conform to a single plan of stomatal construction that is unusual in its extraordinary plasticity: both the number of subsidiary cells and their arrangement vary greatly on a single epidermis, such that the stomata might be classified as paracytic, anomocytic, laterocytic, and intermediate. Such stomatal diversity is uncommon in extant angiosperms but is known from a few Magnoliidae. Many species possess secretory cells comparable to the oil cells of modern Magnoliidae, and a few show the bases of probable uniseriate hairs. None of the cuticle types can be assigned to a single modern family, but several show similarities with Chloranthaceae and Illiciales. These results support the concept that subclass Magnoliidae includes some of the most primitive living angiosperms.

Dispersed cuticles from the Eocene of North America

KOVACH, W. L. & DILCHER, D. L., 1984. Dispersed cuticles from the Eocene of North America. Macerations of organic-rich clay from the Claiborne Formation (Middle Eocene) of Tennessee have yielded a wide variety of well-preserved dispersed cuticles. Details of the epidermal cell patterns, arrangement of the stomata1 complex, trichomes and trichome attachment have made possible the association of some dispersed cuticles with leaf types known from this formation which have similar cuticle, and with modern families. All dispersed cuticles are classified in a morphologic system. Through both our own work and a review of previous investigations we have found that distinct dispersed cuticle types can be recognized and may be used biostratigraphically to characterize geologic strata, palaeo-ecologically to provide insights into environmental reconstruction, and systematically to follow the history of certain taxa.

Juvenoids cause some insects to form composite cuticles

Metamorphosing insects treated with juvenoids may secrete composite cuticles which combine morphological features of two metamorphic stages within the area secreted by an individual epidermal cell. Characters found combined were pigmentation, tanning, surface sculpturing, and microtrichiae. Neighbouring cells frequently form different types of cuticle. Composite cuticles should not be confused with the more common mosaic cuticles, which are composed of discrete areas with different stage-specific morphology (e.g. some larval patches set in an otherwise normal adult cuticle). Treatment of last instar nymphs of Pyrrhocoris apterus (Hemiptera) with a juvenoid induced secretion of composite cuticle which combined larval morphological features with imaginal pigmentation. Cells remained susceptible to composite cuticle induction over an extended period prior to the actual initiation of cuticle deposition. Composite cuticle which contained larval microtrichiae and pupal tanning were induced with juvenoids in the lepidopterans Hyponomeuta malinella, Hyphantria cunea, Spodoptera littoralis, Mamestra brassicae, Pieris brassicae, Aglais urticae, but not in Galleria mellonella. Composite cuticle possessing both pupal and imaginal morphological features was produced with juvenoids in Leptinotarsa decemlineata (Coleoptera). It is suggested that this type of cuticle reveals the secretory capacities of a single epidermal cell when the cellular reprogramming from one developmental stage to the next has been stabilized at an intermediate point by juvenoids.

Cuticular sclerotization in the honeybee (Apis mellifera adansonii)

A micromethod has been developed for quantitative determinations of ketocatechols released by acid hydrolysis from samples of sclerotized insect cuticle, weighing from 0.1 to 5 mg. The method has been used to follow the changes in yield of ketocatechols from five different types of cuticle during honeybee development. Samples from workers, drones, and queens have been analyzed. The increase in yield of ketocatechols is most pronounced during the period of pharate development when abdominal cuticle is stiffened and the cuticular proteins become insoluble.

Some ultrastructural characteristics of mandibular cuticle in an elaterid larva (Coleoptera)

The cuticular walls of the mandibles of larvae of Ctenicera destructor (Brown) have a layer of nonlamellate procuticle with a preferred orientation of cuticular microfibrils and pore canals. This type of cuticle is characteristic of many pterygote adult cuticles but has not been noted in larval cuticles of other cephalic appendages or body sclerites and membranes. This nonlamellate layer is sandwiched between two layers of lamellate procuticle over most but not all of the mandibular base. There is no outer lamellate layer of procuticle in the walls of the mandibular teeth, but the layer of protein epicuticle is exceptionally thick here, comprising about two-thirds of the total wall thickness. These characteristics of the mandibular cuticle are discussed with respect to wall strength, tooth wear, function of mandibular mechanosensilla, and development.

Ultrastructural study of the development of the auditory tympana in the cricket Teleogryllus commodus (Walker)

The cuticle in the tympanal area of immature crickets, Teleogryllus commodus (Walker), is ultrastructurally indistinguishable from that elsewhere on the prothoracic leg. It is only in the pharate adult that changes associated with development of the tympana first appear. In pharate adults and adults the external layer of the tympana consists of a layer of electron-dense material overlying a layer where the electron-dense material is interspersed with cuticle in which the bundles of microfibrils are coarser and more loosely arranged than elsewhere in the leg. The innermost portion of the tympana consists of this same type of cuticle without the electron-dense material. Associated with the appearance of the electron-dense material in the tympana of the pharate adult is a change in the toluidine blue staining properties from blue to deep purple. The reaction of the tympana in acid and base is consistent with their being composed of chitin. There are no major deposits of resilin in the tympana. In the first few days following the imaginal ecdysis the posterior tympanum and underlying trachea come into tight apposition due to the withdrawal of the epidermal cells. The epidermal cells do not withdraw from beneath the anterior tympanum. The surrounding non-tympanal cuticle continues to thicken for several weeks with the result that in the mature adult the posterior tympanum serves as an acoustic window in the thick cuticle of the leg. The functional significance of the anterior tympanum has not been established.

Changes in the structure and composition of the extensible cuticle of Rhodnius prolixus through the 5th larval instar

Changes in the composition of the extensible cuticle through the 5th larval instar of Rhodnius prolixus were measured and related to the physiological and developmental state of the larva. Particular attention was paid to the extractable proteins and their characteristics are related to the plasticisation and stretch of the cuticle during the feeding process. There are eight major soluble proteins in the cuticle; three are acidic and five are basic. A model of the cuticle structure held together by ionic and hydrophobic interactions between the constituents is proposed. Polymorphism as a reason for the large number of proteins in ‘soft’ cuticles is refuted on the evidence available. A novel type of transitory cuticle is formed after the feeding of larvae. The role of this cuticle is discussed and a multiple function proposed for it.

Hormonal control of insect epidermal cell commitment in vitro.

DEPENDING on the hormonal milieu, the insect epidermal cell can express one of several differentiated states manifest by the type of cuticle it secretes. In the Lepidoptera, as long as the juvenile hormone (JH) titre is high, the epidermis secretes larval cuticle periodically in response to ecdysone. When the JH litre declines at the end of larval life1, ecdysone causes the secretion of pupal cuticle. In the tobacco hornworm, Manduca sexta, two distinct releases of ecdysone are necessary for this metamorphosis2,3. The first triggers the cessation of feeding and causes the epidermal cells to switch from a commitment to make larval cuticle to one for pupal cuticle4. After this time JH can no longer prevent pupal differentiation. The second ecdysone release begins 2 d later and causes pupal cuticle synthesis. Consequently, during the time of the first release it is possible to study the events which occur to alter the cellular commitment unhindered by those events involved in the expression of this commitment. I report the hormonal manipulation of this cellular commitment in an in vitro system.

Material properties of arthropod cuticles: The arthrodial membranes

1. On the basis of tensile mechanical properties fibre-reinforced arthropod cuticles can be classified into two main types: one in which the stiffness is provided mainly by the matrix and the other in which stiffness derives largely from the chitin fibres. 2. These two types of cuticle can be related directly to function: the former is relatively hard and stiff and typical of sclerites and thus imparts skeletal rigidity and chiefly subserves a protective function, the latter gives rise to relatively soft and supple, yet flexible materials commonly encountered in arthrodial membrane cuticle. 3. Some cuticles show elements of both of the above types. It appears that these intermediate cuticles are specialized forms and occur as optimizations between the main functions of protection and locomotion, as in caterpillars. 4. It is concluded that a description of arthropod cuticle in mechanical terms is better suited to the understanding of function and is therefore biologically more meaningful than are classifications based on either fibre architecture or histological staining reactions.

"EXTRANUMERARY" CUTICLE DEPOSITION IN PIECES OF LARVAL INTEGUMENT TRANSPLANTED TO A PUPA IN THE SILKWORM BOMBY X MORI.

The author (Kato, 1973b) reported that in Bombyx mori, pieces of larval integument, if transplanted to a pupa, produced two layers of cuticle during the metamorphosis of the host pupa to an adult. In the present transplantation experiments, deposition of the two layers of cuticle was temporally examined to determine the timing of the two depositions, compared with the host's cuticle deposition, using 0-day-old fifth-instar or 1-day-old fourth-instar larvae as donors. In the transplant the first deposition occurred within 4 days of transplantation, with the second deposition at 6 to 8 days, while the host began cuticle deposition 6 days after receiving the transplant. These results show a failure of simultaneous deposition between the transplant and the host. These moulting events in the transplant, e.g., the fairly early appearance of the first cuticle and temporally-separated ecdyses, are discussed in view of the change of ecdysone titer in the host. Furthermore, the temporal pattern of cuticle deposition in the transplant appeared to have a definite relationship with the type of cuticle deposited.