Biomedical subjects
Publications and source records attributed to P N Dilly.
H.R.P. technique has been used, and shown usefull in the retrograde tracing of the motor neurons from both main branches of the hypoglossal nerve. Traced motor neurons were observed at spinal levels and a portion of the brain stem slightly below the pyramidal decussation to a plane where the inferior olivary nucleus begins to disappear.
Computer-simulated analysis of cell migration was attempted with the aim of improving the discriminative characterization of the in vitro locomotory behaviour of normal and neoplastic cells and verifying a concept of cell movement regulation proposed earlier. It suggested that cell membrane activity and distribution of resting periods along the cell trajectory could be introduced with advantage among the migration parameters; this appeared to be a promising refinement on the standard methodology. Moreover, it was inferred that setting up critical, instead of optimal, conditions for cells in culture should reveal behavioural differences otherwise hidden.
Previous attempts by others to measure the wettability of the corneal epithelium concluded that the surface was strongly hydrophobic, but used methods which seem likely to damage the epithelial cell surface. These experimental techniques were repeated and the effects on the surface analysed by scanning electron microscopy. It is concluded that such methods cannot establish either the hydrophobicity or hydrophilicity of the cornea.
After oral administration of tetracycline fluorescence has been detected in biopsy specimens taken from human and animal conjunctiva. The fluorescence is not uniform but appears to be concentrated in the goblet cells, around the blood vessels, and in a thin film on the external surface of the epithelium. Immersion studies suggest there is a selective binding to the surface of the conjunctiva.
The layer of the tear film in contact with the conjunctiva is mucus. This mucus comes from two sources, the conjunctival goblet cells and the subsurface vesicles. These vesicles are found just below the surface of the conjunctival cells. They contain long chain mucus glycoprotein molecules that are joined to the vesicle membrane. The vesicles fuse with the surface membrane of the conjunctival cells and expose their mucus glycoprotein chains to the overlying mucus. Chemical and physical bonds between the two types of mucus help to bind the mucus layer to the conjunctiva. The vesicle membrane becomes incorporated in the cell membrane and supplies the membranes for the microvilli that cover the exposed surface.
The superficial cells of the epithelium make a mucoprotein with long chemical chains and package it in the subsurface vesicles. Subsurface vesicles fuse with the cell membrane and the side chains thus exposed join with the overlying mucus to anchor the mucus to the epithelial layer. The membranes surrounding the subsurface vesicles become incorporated in the cell membrane and provide the extra membrane required for the sprouting of microvilli. The goblet cells secrete the overlying mucus layer.
This paper describes changes in the ultrastructure of the human conjunctiva which follows its denervation. The changes are mainly seen in the mucus-producing subsurface vesicles, the surface microvilli, and the intercellular spaces. Some tentative suggestions are made as to how these changes may influence the stability of the tear film in the anaesthetic state.
The surface features of atrophic rhinitis are shown and it is suggested that these explain the majority of symptoms. It seems clear that any lesion preventing the formation or maturation of large numbers of motile cilia, or the production of mucus capable of forming confluent sheets suitable for continuous propulsion, may cause atrophic rhinitis. In both familial and idiopathic forms of the disease, both abnormalities are present. It would be most interesting to know the ultrastructure of the cilia in transverse section of this condition. Transverse electron microscopic studies in Retinitis Pigmentosa, Usher's syndrome and Kartagener's syndrome now becoming known as the low cilia motility diseases show clearly the primary lesions in the micro-tubules and dynein arms of the cilia. A similar transmission electron microscopic study in atrophic rhinitis may show the fundamental cilial lesions. Surgical closure of the nasal passages has much to offer the patient with severe symptoms as the clinical features of the disease improve with the increasing normal micro-anatomical features demonstrated in this paper as a result of closure. This improvement in structure is not in all cases sufficient to fulfil the above criteria so a complete cure is improbable in the majority of cases.
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Rhabdopleura has densely ciliated tentacles and cephalic shield. These cilia are of two sorts, ordinary cilia and those bearing paddle-like swellings. These swellings, about 1 micron across, are in the ciliary membrane. The axoneme bundle within the cilium remains intact, keeping the usual spatial arrangements, except that in the swelling its overall diameter is reduced. It is suggested that the mechanism for moving the paddle-like swellings along the length of the cilium is the releasing and reattaching of the side filaments from the axoneme to the ciliary membrane.
The surface of the Rhabdopleura zooid is ciliated. The cilia of the cephalic shield and tentacles have paddle-like swellings of the shaft. These swellings are usually about 0.6-1 micron in diameter and most frequently found in the distal 1-2 micron of the ciliary shaft. Others are found in other positions along the length of the cilium and it is suggested that at least some of these swellings represent material transport within the cilium. Paddle shaped cilia are probably more efficient than normal cilia in moving water and food particles. If these cilia are involved in the building of the tubular coenecium then their distribution suggests that the tentacles as well as the cephalic shield are actively involved in tube building.
The statoliths of Sepia officinalits, Octopus vulgaris, Alloteuthis subulata and Taonius megalops have a smooth outline, but an irregular shape. They have projections and indentations. The statoliths from a pair of statocysts are usually quite similar in size and shape, and the general pattern is probably maintained throughout the size range of the species. Statoliths from large animals are marginally larger than those from smaller ones. The statolith usually occupies only a small part of the cavity of the statocyst, and it is situated in the anterior part of the statocyst. They are joined to the macula by hairs extending from it. These hairs are very delicate and easily broken during preparation of the specimens. The hairs are much longer and narrower than the receptor cilia of the macula. The receptor cilia are enclosed within holes in the tangled hairlike anchoring fibrils. The statolith is made up of crystalline subunits, the statoconia. The crystals vary in size, they are usually elongated, hexagonal with pointed ends. The statolith consists of a closely packed mass of these crystals, sometimes they are irregularly arranged, where in others they are stacked with their long axes parallel. In Sepia officinalis and Taonius megalops, the crystals are arranged in regular shaped packets and these packets of crystals are stacked together. These larger subunits are not always arranged in a regular way, and their major axes can be organised in several different ways. The size and outline of these large subunits do vary in different parts of the statolith. The external surface of the statolith is macroscopically smooth. Over some parts there is a surface layer covering the rod-like crystals that make up the major bulk of the stone. In other regions, the surface is rough at a microscopic level, the roughness is produced by the exposed ends of the filamentous crystals. The crystals are composed of calcium carbonate in the form of aragonite.
The coenecium of Rhabdopleura consists of a series of tubes, some erect and some repent. These tubes are composed of rings, one stacked within another. The rings are smooth on the inside surface and rough outside. Newly laid down rings are thin and smooth on both surfaces, fibrous material is laid down on the external surface during growth in thickness by the cephalic shield of the zooid. The erect tubes remain discrete, but the repent tubes, which are attached to the substratum can become incorporated in a mass of secreted material. The external vertical fibres cross several rings and probably serve to anchor the stack. Besides these fibrils that run for several segments, there are other shorter fibres that run along the length of each cylindrical ring, and are not continuous across the rings. These long and short fibres have features in common with those found in the graptolites.
A single layer of cell secrets the hard cephalopod beaks. The beccublasts are tall columnar cells that separate the beak from the surrounding buccal muscles, and must serve to attach these muscles to the beak. Within the cell layer there are three types of cells. The first, and most frequently found contain cell-long fibrils. These fibrils may have contractile and tensile properties. Complex trabeculae extend from the beccublasts into the matrix of the beak. The fibrils are attached to these trabeculae and at the other end of the cells they are anchored near to the beccublast-muscle cell interface, closely associated with the muscles that move the beak. The second group of cells contain masses of endoplasmic reticulum the cysternae of which are arranged along the long axis of the cell. These cells also contain dense granules and are probably the major source of beak hard tissue. It is probable that each cell secretes its own column of beak hard tissue. The third group of cells cells contains a mixture of fibrils and secretory tissue. In the beccublast layer there are changes in the proportion of the three types of cells depending upon the region sampled. In the region where growth is most active there are mostly secretory cells, whereas near the biting and wearing tip there are mainly anchoring type cells.
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Rhabdopleura has an overwintering stage that consists of two layers of cells surrounding a central yolk mass. This cellular part is surrounded by a thick electron dense capsule which is secreted by the bud itself. The capsule is probably impervious and protective to its contents. Blood vessels join the buds to the zooids of the colony. They form the probable route of transfer of yolk from the zooids to the dormant bud. The capsule of the dormant bud has some structural features in common with the black stolon of the adult zooids. The black stolon is probably formed in a manner similar to that which made the fusellar fabric of the periderm of fossil graptolities.
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