Biomedical subjects
J Caley
Publications and source records attributed to J Caley.
Ultrastructural studies of the cysticercoid of moniezia expansa (Anoplocephalidae) with special reference to the development of the cyst.
Cysticercoids of the sheep tapeworm Moniezia expansa have been grown in oribatid mites in the laboratory. Three species of mite became infected: Xenillus tegeocranus, Platynothrus peltifer and Euzetes globulus, the latter not previously recorded as a host of anoplocephalines. Cysticercoids aged 15 and 28 weeks were examined with the electron microscope. Four distinct types of cells were found in the 15-week cysticercoid. Subsequent cyst development involves a transformation from a cellular to a mainly fibrous structure. The fibres, arranged in three layers, resemble collagen fibres described elsewhere. The outer epidermis of the cyst is replaced by an amorphous, electron-dense outer coat whose nature is unknown. The inner part of the cyst becomes condensed to a myelin-like structure. The scolex develops features characteristic of the adult tapeworm.
A comparative study of the two alternative larval forms of Hymenolepis nana, the dwarf tapeworm, with special reference to the process of excystment.
Studies of the cysticercoids of Hymenolepis nana from insects and from mouse villi revealed important differences in cyst structure and function. The insect form resists low pH unless treated with bile salts which render the cyst permeable and reduce infectivity to mice. Bile salts are not essential for scolex activation. Activation is inhibited by pH 2.5 and under and by 1% succinic acid up to pH 4.0. The importance of scolex immobility and energy conservation in relation to cyst impermeability is discussed. The villus cysticercoid has no special insulating layer. It is vulnerable to low pH and cannot infect mice orally. Bile salts are without effect and excystment occurs unaided by external agents. The structural differences between the two forms revealed by the electron microscope may be attributed to changes in the relative rates of development of the various tissues.
Sexual reproduction in the monogenean Diclidophora merlangi: tissue penetration by sperms.
Copulation between pairs of adult Diclidophora merlangi detached from the host was frequently observed. The spined penis of one animal always attaches to a second worm at a latero-ventral position posterior to the genital openings. There is no vagina. The sperms travel between the cells of the recipient to reach the seminal receptacle. The ultrastructure of the sperm is described. Positions of adult D. merlangi on the gills of the host would facilitate pairing for sperm transfer.
In vitro hatching of the tapeworm Moniezia expansa (Cestoda: Anoplocephalidae) and some properties of the egg membranes.
In vitro studies revealed that the hatching of oncospheres of Moniezia expansa requires the mechanical breakage of the eggshell and subshell membrane and enzymic digestion of the pyriform apparatus. Removal of the outer two egg membranes elicits the activation of most oncospheres. Between pH 5.0-7.8, there is no significant difference in numbers of oncospheres activated by eggshell removal and the addition of sodium bicarbonate has no effect. Solutions of more extreme pH values (2.0 and 10.0) are harmful and render oncospheres immobile. The subshell membrane forms a barrier to the passage of water in an osmotic gradient and to several molecular and ionic substances. Between the eggshell and subshell membrane is a layer of droplets which have a strong affinity for Sudan stains and which are partially removed by lipase. The eggshell is resistant to a variety of proteolytic enzymes, amylases and lipase. The pyriform apparatus is digested by chymotrypsin and pepsin, though not by trypsin. Both eggshell and pyriform apparatus are dissolved by solutions of sodium sulphide and sodium hypochlorite, indicating that their structures are stabilized by disulphide bonds and other covalent linkages.