J. Carter Rowley

A simple procedure for mounting wrinkle-free sections on formvar-coated slot grids.

This paper describes a simple technique for consistent production of clean, unwrinkled, flat thin (500-1000 A) sections for TEM and thick (1/2-1 micron) sections for HVEM mounted on Formvar-covered slot grids for use in conventional and high voltage electron microscopy. The technique centers around use of a Formvar-covered aluminum supporting rack onto which slot grids that contain sections suspended in water are placed.

Electron microscopy of human olfactory epithelium reveals a new cell type: the microvillar cell.

The olfactory epithelium of mammals is generally considered to consist of 3 cell types: basal cells, supporting (sustentacular) cells, and ciliated olfactory receptors. We have completed a detailed ultrastructural study of the fine structure of the human olfactory mucosa. In our electron microscopic observations of biopsies of human olfactory epithelium taken from normal, consenting volunteers under local anesthesia, we have consistently observed a fourth cell type, the microvillar cell, located near the epithelial surface. The apical end of these flask-shaped, electron-lucent cells gives rise to a tuft of microvilli that project into the mucus layer lining the nasal cavity. The cell body itself contains bundles of microfilaments, mitochondria, a well-developed smooth endoplasmic reticulum, a prominent Golgi complex, electron-dense vesicles that resemble lipofuscin granules, free ribosomes, and occasional cisternae of the rough endoplasmic reticulum. A thin, axon-like cytoplasmic process extends from the basal pole of the cell and travels through the epithelium toward the lamina propria. Although there is no physiological evidence that bears upon the function of the microvillar cell, its ultrastructure suggests it may be a bipolar sensory neuron. Based upon morphological and phylogenetic considerations, the authors speculate the microvillar cell represents a second morphologically distinct class of chemoreceptor in the human olfactory mucosa.

The fine structure of the cockroach subgenual organ.

This paper describes the fine structure of the cockroach subgenual organ, a complex ciliated mechanoreceptor that detects vibrations in the substrate upon which the animal stands. Located beneath the knee in each walking leg, the cockroach subgenual organ is a thin, fan-shaped flap of tissue slung across the dorsal blood space of the tibia at right angles to the legs long axis. It is innervated by approximately 50 chordotonal sensilla. The fine structure of the chordotonal sensilla is is described in detail; possible transducer sites are discussed.

High voltage and scanning electron microscopy of the site of stimulus reception of an insect mechanoreceptor

This paper describes the ultrastructure of the site of mechanical stimulation of the cockroach campaniform sensillum. The cuticular “cap” of the sensillum has been studied by scanning electron microscopy (SEM) and high voltage transmission electron microscopy (HVEM). The SEM was used to study the upper and lower surfaces of the extracellular chitinous cap. The internal composition of the cap was analyzed by HVEM. Two significant structural features were observed: (1) the dome of the cap contains a reinforcing ring, the “cuticular collar,” as an integral part of its substructure; and (2) the dome of the cap is firmly attached to the surrounding exoskeleton at two specific points located at each end of the oval dome. The functional implications of these two structures is discussed.

A somatotopic organization of groups of afferents in insect peripheral nerves

Sensory axon projections in the main leg nerves of two orthopteran insects, the cockroach Periplaneta americana and the grasshopper Melanoplus bivittatus, were studied by observing patterns of axonal degeneration after ablation of different leg segments. The patterns of degeneration seen in transverse sections of the leg nerves, close to their entrance to the central nervous system (thoracic ganglion) show that sensory axons occur in constant positions in the leg nerves. When distal leg segments are removed, a discrete area of degeneration is found in the leg nerve along its posterior edge. More proximal ablations produce larger areas of degeneration that progressively extend into the anterior half of the nerve. A comparison of the patterns of degeneration produced by different leg ablations shows a posterior to anterior laminar arrangement of groups of sensory axons that corresponds to a distal to proximal map of the leg. This mapping has been confirmed by localized ablations of small groups of leg sensory receptors.

The control of ciliary movements: an application of the cusp catastrophe.

Abstract The main purpose of this paper is to describe the mutual control relations between ciliary movements and molecular events in the axoneme. These control relations are expressed mathematically through a cusp-catastrophe description between angular movements and active sliding. The parameters are defined so that they are widely applicable and accessible to experimentation. A choice of parameters is tested on the basis of Satirs studies on active sliding, the energetics of ciliary beating, and the dependency on ATP for beat amplitude. For all these cases a good predictive fit is found. Further application and connections of the proposed control model are discussed.