Staining of the elastic fibers in insect connective tissue after tannic acid/glutaraldehyde fixation

The metathoracic wing-hinge chordotonal organ of an atympanate moth, Actias luna (Lepidoptera, Saturniidae): a light- and electron-microscopic study

The structure of a simple chordotonal organ, the presumed homologue of the noctuoid moth tympanal organ, is described in the atympanate moth, Actias luna. The organ consists of a proximal scolopidial region and a distal strand, which attaches peripherally to the membraneous cuticle ventral to the hindwing alula. The strand is composed of elongate, microtubule-rich cells encased in an extracellular connective tissue sheath. The scolopidial region houses three mononematic, monodynal scolopidia, each comprised of a sensory cell, scolopale cell, and attachment cell. The dendritic apex is octagonally shaped in transverse section, its inner membrane lined by a laminated structure reminiscent of the noctuoid tympanal organ 'collar'. A 9 + 0-type cilium emerges from the dendritic apex, passes through both the scolopale lumen and cap, and terminates in an extracellular space distal to the latter. Proximal extensions of the attachment cell and distal prolongations of the scolopale cell surrounding the cap are joined by an elaborate desmosome, with which is associated an extensive electron-dense fibrillar plaque. Within the scolopale cell, this plaque constitutes the scolopale 'rod' material. The data are discussed in terms of both the organ's potential function, and its significance as the evolutionary prototype of the noctuoid moth ear.

Lamellar bodies in differentiating insect tissues during basal lamina formation as revealed by tannic acid

Tannic acid penetrates differentiating tissues differentially resulting in variable contrast, extraction and dense bodies with a lamellar substructure. The penetrability appears to correlate with the existence and/or robustness of a basal lamina. In the male genital tract, probably of mesodermal origin, tannic acid penetrates the epithelium until there is a basal lamina, but in the ectodermal bursa copulatrix it does not penetrate since there is always a basal lamina. The lamellae of the dense bodies have a center-to-center spacing of 4.65 +/- 0.025 nm, dimensions which resemble those of phospholipids.

The ultrastructure of the byssal apparatus of a mussel. V. Localization of collagenic and elastic components in the threads

Ultrastructural and cytochemical studies have been carried out on the proximal part of byssus threads (TPP) in an attempt to localize collagenic and elastic components. The results show that TPP autoclaving followed by hot alkali treatment causes the extraction of about two-thirds of hydroxyproline and the parallel removal of most of the matrix, leaving filaments unaffected. Moreover the results of the staining reactions signaletic for elastic tissues indicate that TPP filaments contain glycoproteins with a reactivity similar to that of many invertebrate elastic tissues. On the basis of these morphological findings, it seems reasonable to suggest that collagen may be located in TPP matrix, while filaments could be responsible for the elastic properties.

Golgi complex beads in vertebrates and their relationship with clathrin coats

Addition of tannic acid to the primary glutaraldehyde fixative and the viewing of thin sections by stereo electron microscopy greatly simplifies the detection of vertebrate cell Golgi complex beads which are otherwise difficult to see since they do not stain with bismuth. These results confirm the generality of conclusions from experiments on arthropod beads which are easily observed because of their bismuth affinity. In vertebrate and arthropod cells, bead rings encircle the base of forming transition vesicles below the growing portion of the vesicle that is covered with a clathrin coat. Their unique position at such a sharp functional and structural boundary in intercompartmental transport suggests that the bead rings may specify a select region of rough endoplasmic reticulum devoid of ribosomes where clathrin coats can induce transition vesicle formation and prevent intermixing of the elements of a returning transition vesicle.

The use of glutaraldehyde and tannic acid to preserve reconstituted collagen for electron microscopy

The effects of glutaraldehyde and tannic acid on the axial periodicity of collagen have measured. Both fixatives produce axial shrinkage of the collagen but whereas glutaraldehyde produces 7% shrinkage, tannic acid produces only 2% shrinkage. The technique of carbon/platinum shadowing was used to estimate the extent to which the collagen fibrils flatten down when they are dried onto grids for electron microscopy without prior embedding and sectioning. The influence of fixation was studied and it was found that minimum distortion occurred when both tannic acid and glutaraldehyde were used to preserve the protein structure.

Morphology and design of the extensible intersegmental membrane of the female migratory locust

The morphology of the extensible intersegmental membrane (i.s.m.) of the female Locusta migratoria migratorioides is dictated by three main requirements: (a) high extensibility (1500%), (b) low stiffness (5 X 10(3) Pa), (c) low Poisson ratio in the plane of the cuticle (0.01 or less). These requirements can be met only orientating the chitin orthogonally to the direction of extension and having the protein phase uncross-linked and of very low modulus. The Poisson ratio requirement also implies that for the material to be extended at constant volume extreme thinning must occur during extension, giving rise to high shear strains in the direction of extension. The ultrastructure and morphological elements are modified from 'normal' cuticle such as to provide for high extensibility (due to unfolding) of the epicuticle and epidermal cells and a complex system of intracuticular fibres which are probably necessary to retain the topology of the components during high shear straining. No new morphological elements are adduced in this study but the extreme adaptability of those established for other cuticles is illustrated.

Elastic tissue in the limiting membrane of the human seminiferous tubule

The structure and distribution of elastic tissue were studied in the limiting membrane of the seminiferous tubule from normal human testis. The elastic and elastic-related fibers (oxytalan and elaunin) were recognized by their tinctorial and ultrastructural characteristics. The connective structures of the limiting membrane, including the fibrotubules and the amorphous material of the elastic system, were studied after tannic acid-glutaraldehyde fixation. Fibrotubules (oxytalan fibers) were observed in almost all intercellular spaces of the limiting membrane, closely related to the contractile cells; the elaunin fibers (patches of amorphous material surrounded by bundles of fibrotubules) were evident in the outermost layers. The function of this system of elastic tissue and myoid cells is discussed, considering the permeability membrane and the role of the myoid cells in the elastogenesis and contractility of the seminiferous tubule.