Observations on the gastric epithelium of ascidians with special reference to Styela clava

Summary Transmission electron microscopy shows the gastric epithelium of Styela clava to comprise at least three distinct cell types. Ciliated mucous cells which form the crest of each stomach ridge produce mucus by an unexpected route. Vacuolated cells lining the ridge sides appear to be absorptive in function. Gastric enzymes are produced by typical protein secreting cells scattered amongst the vacuolated cells. Undifferentiated cells are found in the crypts between ridges. The structure and function of the gastric epithelium in Styela is discussed with special reference to the wider concepts of ascidian gut organization.The author is grateful to Mrs. L. Rolph for technical help with scanning electron microscopy and Mr. J. Calvert and Mr. R. Jones for assistance with the transmission electron microscopy. Animals were collected through the kind offices of Mr. J. Sturges and other staff of the Admiralty Marine Trials Station, Portsmouth. This research was carried out during the tenure of SRC grant No. B/RG 82919 -The localization of polypeptide hormones in the pharynx and gut of Protochordates     

The epidemiology of hydatidosis with special reference to the Mediterranean area.

In the Mediterranean area 2 subspecies of Echinococcus granulosus exist: E. g. equinus and E. g. granulosus. The latter is divided into sheep, cattle, pig and camel strains, the adult forms of which mainly occur in farm-dogs but sometimes in wild canidae. Some of these strains can infect man: namely, the sheep and the pig strain. The infectivity of the cattle strains for man is not certain. The epidemiological cycle is mainly a rural one, but it can become sylvatic or even urban. Thus, the epidemiological features of hydatidosis in the Mediterranean area are not basically different from the general epidemiology of the disease. But extensive rearing of sheep, combined with the carelessness and ignorance of people and with some particular habits, favours the maintenance of the infection.     

Observations on the dental anatomy of piranhas (Characidae) with special reference to tooth structure

A study of the tissues of the teeth and jaws in piranhas, using the scanning electron microscope and various techniques of light microscopy, revealed many dental adaptations related to the specialized feeding habits of these carnivorous fishes. The dentition is primarily sectorial, although some anterior teeth may be used in grasping. The scissor-like rows of teeth are maintained by the specialized pattern of tooth replacement. The bones of the jaws and the tooth attachment support the teeth very firmly. In its structural organization, the enameloid covering the teeth closely resembles that on the sectorial teeth of sharks and is adapted to the probable stress patterns set up in biting.     

Myocardial infarction in young women with special reference to oral contraceptive practice.

Sixty-three women discharged from hospital with a diagnosis of myocardial infarction and 189 control patients were studied. All were under 45 years of age at the time of admission. Current oral contraceptive use, heavy cigarette smoking, treated hypertension and diabetes, pre-eclamptic toxaemia, and obesity were all reported by, and type II hyperlipoproteinaemia was found more often in, patients with myocardial infarction than their controls. The relationship between myocardial infarction and oral contraceptives could not be explained in terms of an association between the use of these preparations and the other factors. The combined effect of the risk factors was clearly synergistic.     

Observations on the prevalence and incidence of ergot disease in Great Britain with special reference to open-flowering male-sterile cereals

Ergot (Claviceps purpurea) of grasses is prevalent throughout Britain. The disease also occurs regularly in most cereal varieties but generally is of low incidence. Incidence is much greater in open-flowering and male-sterile cereals, with the infection seeming to come, initially, from the large reservoir of inoculum amongst grasses. The production of F₁-hybrid cereal seed, which necessitates the use of male-sterile lines, could therefore be jeopardised.     

Observations on the attachment by the monogenean, Anoplodiscus australis, to the caudal fin of Acanthopagrus australis

The unarmed haptor of Anoplodiscus australis erodes the epidermis and attaches to the basal lamina above the stratum compactum in the caudal fin of Acanthopagrus australis by an eosinophilic, weakly PAS-positive and strongly toluidine blue-positive secretion. Ultrastructural evidence shows that the adhesive secretion, in the form of rod-shaped bodies, is produced by subtegumentary cells that connect by ducts to the thin, ventral syncytial tegument of the haptor; these bodies pass into the tegument, then coalesce in the host-parasite interface. This means of attachment has developed by an enhancement and regional specialization of the subtegumentary secretory cells associated with a syncytial tegument in monogeneans and some other platyhelminths. The available evidence indicates that the adult parasite is permanently attached.     

Observations on root and stem contraction in cycads (Cycadales) with special reference to Zamia pumila L.

Cycads are pachycaulous plants possessing either aerial and columnar (arborescent) stems or subterranean and tuberous fleshy stems. In some taxa, such as Zamia pumila and Stangeria eriopus , the vertical shoots are subterranean; the shoot apex usually remains underground even though new shoot increments arc added as a result of leaf development. The external surface of these stems has a winkled appearance in the distal regions and the height of the leaf scars decreases basipetally This is because both the fleshy tap root and the stem contract, pulling the shoot underground. This contraction results from the collapse of horizontal rows of cells in both the pith and cortex. The vascular cylinder which appears straight in longitudinal sections becomes sinuously distorted as this collapse of cells occurs.