Leishmania major: in vitro ultrastructural study of the paraxial rod of promastigotes.

The flagellum of Leishmania major promastigotes has an intraflagellar structure known as the paraxial rod (PAR) which extends from a point halfway in the flagellar pocket to the tip of the flagellum, lying opposite the axonemal microtubule doublets 4-7. An expansion of the axonemal plasma membrane envelops the PAR and may provide desmosomal attachment at the orifice of the flagellar pocket. The complex organization of the 4-6 nm thick filaments in the PAR was studied by us in cross, oblique, longitudinal and tangential sections by electron microscope. These filaments are disposed in two parallel lamellae, one alongside the axoneme (ca. 45 nm thick), and the other alongside the plasma membrane (ca. 65 nm thick), with an interlamellar gap of about 22-28 nm. In each lamella, 8-12 parallel series of longitudinal filaments at ca. 30 nm intervals interdigitate with coplanar parallel series of oblique filaments at ca. 25 nm intervals and inclined to the long axis of the flagellum at ca. 48 degrees, and ca. 55 degrees, in the inner (paraxonemal) and outer lamella, respectively. The parallel filaments in each of the longitudinal and oblique series are spaced at ca. 8 nm intervals. They are cross-striated at ca. 30 nm intervals by transverse filaments which terminate occasionally on adjacent axonemal microtubules 5 and 6 in the inner lamella, and the plasma membrane in the outer lamella. Extending across the interlamellar gap is a set of parallel rows of 7-12 nearly parallel filaments at ca. 20 nm intervals. The part of the flagellar plasma membrane enclosing the PAR has a subplasmalemmal cytoskeleton consisting of a layer of longitudinal 2 nm filaments at 8 nm intervals, obliquely striated by parallel 2 nm filament doubles at ca. (-65) degrees with the long axis of the flagellum and ca. 20 nm periodicity. Each filament doublet stria apparently gives origin to collinear short filament doublet extensions that curve into juxtaposed meshes of the outer lamella. Microtubules of the axonemal doublets 5 and 6 are connected to electron-dense (ca. 12 nm thick) strips of the inner lamella of the PAR by longitudinal series of ca. 4 nm cross-links across a ca. 12 nm cleft.

Conjunctival ophthalmomyiasis caused by the sheep nasal botfly (Oestrus ovis)

Three patients had conjunctival ophthalmomyiasis caused by the ovine nasal botfly. All patients had a sudden onset of redness, tearing, and foreign-body sensation of the affected eye. One to nine Oestrus ovis first-instar larvae were removed from the bulbar or palpebral conjunctiva of each patient. Symptoms and clinical signs resolved after mechanical removal of the larvae. Specific taxonomic diagnosis of O. ovis larvae was determined on the basis of characteristic conformation of the terminal end of the larval caudal segment as seen by use of light microscopy.

A device for serially mounting 0.5-2.0 micrometer sections of 1-2 millimeter epon embedded tissue blocks for light microscopy.

The construction and operation of a simple device for serially mounting small Epon sections for light microscopy are described. This device allows the middle portion of the slide to serve both as a shallow reservoir behind the knife edge for flotation of serially oriented sections, and as a miniature hot plate for the subsequent flattening and adhesion of the sections. The advantages of this device, which gave consistently good results with Epon embedded Argas (Persicargas) arboreus tick tissues, are discussed.

Ultrastructural study of a corneal keloid.

A 69-year-old man developed keloid overgrowth on his left cornea in response to an injury from a fingernail. The lesion was removed by superficial lamellar keratectomy and was studied by electron microscopy, and light microscopy after immunoperoxidase staining for actin. The surgical specimen revealed disorganised, anteriorly atrophied and posteriorly vascularised connective tissue stroma. The epithelium was oedematous, thin, non-keratinised, and contained cells with features of myoblastic differentiation. Stromal fibroblasts were found in several distinct ultrastructural forms including young active fibroblasts, myofibroblasts, inactive fibroblasts (fibrocytes) and fibroblasts with prominently fibrillar cytoplasm. Fibroblasts with glycogen storage and/or pseudonuclear inclusions were also seen. Macrophages and lymphocytes were scattered in the stroma, and intact nerves were also present. An irregular 2-65 microns band of 10 nm filament meshwork existed at the posterior border of the keloid stroma, and deep localised patches of climatic degeneration were detected.

Orbital myiasis.

Invasion of the orbit by dipterous fly larvae is a rarely reported from of myiasis. We present a 65-year-old man with orbital myiasis caused by the tissue obligatory larvae of the Old World screw-worm fly Chrysomyia bezziana Villeneuve. Larvae were found invading the orbital apex and exenteration was carried out to prevent intracranial invasion. In this case of orbital myiasis, CT scanning was used to document the extent of intraorbital invasion. To our knowledge, this is the first reported case of ophthalmomyiasis caused by C. bezziana.