An autoradiographic study of periodontal development in the mouse.

Tritiated thymidine was injected into 10- and 13-day-old mice because at this age the third molar is at the appropriate stage of development. At set intervals, the mice were killed and the distribution of labeled cells within the dental papilla and follicle examined. The change in labeling index with time was measured for defined areas in the papilla and follicle. It was shown that, during the late bell stage of development, cells moved from the papilla into the follicle. It was concluded that the pulp, rather than the investing layer of the follicle, is the source of the periodontium and that growth of the pulp and periodontal tissues could generate an important force contributing to tooth eruption.

Physical conditions during batch culture of hybridomas in laboratory scale stirred tank reactors.

Due to the nature of animal cell suspension culture, physical conditions during growth such as pH, pO2, pCO2, agitation and aeration are inter-related and can exhibit individual or combined effects on cells. Evaluation of their influence on hybridoma growth and monoclonal antibody production can only be achieved by the use of well-instrumented stirred tank reactors. To determine the effect of the various physical conditions, mouse hybridomas, excreting antibody specific for human IgG, have been cultured in a 2 litre mechanically agitated round bottomed glass vessel, equipped with facilities to monitor and control these parameters during cell growth. Batch culture has been carried out at 36 degrees C in medium supplemented with 5% foetal calf serum (FCS). Clones have also been grown successfully with 2% FCS additions and in serum free medium, after careful adaptation periods. At least two clones have been assessed for comparative purposes.

Techniques of tracheostomy for intensive care unit patients.

The author and his colleagues believe that the surgical technique used constructing a tracheostomy can have a profound effect on the safety and care of patients in the intensive care unit particularly in the first few days after the operation. The Björk procedure is commended to the surgeons.

Acute epiglottitis and severe croup. Experience in two English regions.

The case histories of 50 children who required tracheal intubation for epiglottitis or croup in two English regions have been reviewed. The incidence of severe croup was different in the two regions. The presentation of epiglottitis was variable, and the correct diagnosis was frequently made only at laryngoscopy. Unexpected and rapid deterioration occurred in both diseases, and cyanosis was commonly present on hospital admission and at laryngoscopy. Two children required planned tracheostomy and there were two deaths. The principles of safe management are discussed.

A new mechanism for transitory, local endocytosis in photoreceptors of a spider, Dinopis.

Intermediate segment outgrowth (ISOs) are transitory specialisations of the plasma membrane of intermediate segments of the posterior median photoreceptors of Dinopis. Local regions form outgrowths into the glial partitions separating the receptors and remain connected to their parent intermediate segments by narrow necks. ISOs, only a few micrometers in diameter, are sites of intense endocytosis. Coated pits in their plasma membranes give rise to saccular internalisations. Unusual, slender, endocytotic tubules either pinch off coated vesicles, or become detached to yield a tubular detritus. Products of endocytosis are assembled to yield multivesicular and dense bodies, which are usually surrounded by smooth saccules derived from the endoplasmic reticulum of the intermediate segment. ISOs also contain arrays of tubules, thought to be stacks of haemocyanin molecules. There are usually at least 10 times the number of empty ISOs as full and active outgrowths. The number of active ISOs increases rapidly at dawn to peak at about 3 h after sunrise and then rapidly declines. The present sample suggests that the number of empty ISOs increases steadily throughout the day. Thus, ISOs turn over and are probably rapidly formed and short-lived. The contents of ISOs are observed to be evicted into the intermediate segments, where they presumably join the population of secondary lysosomes and are digested. The cyclical activity of ISOs is greatest after shedding of rhabdomeral membrane at dawn (Blest 1978). ISOs are thought to be concerned with the return to the receptors of a minor fraction of rhabdomeral material lost to extracellular space during shedding of the microvillar membrane.

The sources of acid hydrolases for photoreceptor membrane degradation in a grapsid crab.

Dawn photoreceptor breakdown in the crab Leptograpsus variegatus is analysed at the ultrastructural level. Coated vesicles derived from microvilli are assembled as mutlivesicular bodies (mvbs), which degrade to multilamellar bodies (mls) and are lysed. Cytochemical markers for hydrolases were a fluoride-inhibited beta-glycerophosphatase and a fluoride-insensitive p-nitrophenyl phosphatse, with indistinguishable distributions when localised at pH 5.0. These enzymes are injected into the secondary lysomes from two sources: (i) immediately after dawn Golgi bodies are highly active, and differentiate a transtubular network, from which tubules and vesicles detach, and can be seen fusing with mvbs and mlbs. (ii) Saccules derived from the rough endoplasmic reticulum (RER) provide a second source and are most often seen in association with late mlbs. Both kinds of primary lysosome rare give AcPh-positive responses when free in the cytosol, but are seen to do so as they make contact with their secondary lysosomal targets. Lipid droplets and lipofuscin bodies are interpreted as the residual products of breakdown. These results are discussed in relation to previous findings on photoreceptor membrane breakdown in a dinopid spider. Attention is drawn to the implied diversity of organisation of lysosomal compartments in receptors which internalise membranes of similar compositions.

Pulmonary embolism. Prophylaxis diagnosis and treatment.

The natural history diagnosis and immediate treatment of patients suffering from pulmonary embolism has been discussed. Anaesthetists should use their influence to bring about a high standard of prophylactic care against deep venous thrombosis and consequently of pulmonary embolism. They are likely to be involved in the resuscitation and treatment in intensive care units of those cases who suffer from major symptoms and massive emboli and some of them will rarely be involved in anaesthetising for pulmonary embolectomy aided by cardiopulmonary by-pass and, less rarely, for IVC ligation or plication and venous disobliteration. Anticoagulant drugs appear to limit the mortality of pulmonary embolism to 5%. The mortality of IVC ligation or plication varies in different reports from 2 to 50%; it should therefore be reserved for the special indications which have been discussed. There is also an incidence of recurrent pulmonary embolism after IVC ligation and plication and leg troubles from stasis in about 30% of cases. Streptokinase is usually indicated in the immediate treatment of major pulmonary emboli which cause shock and severe distress with an immediate threat to life. In hospitals having access to cardiopulmonary by-pass, pulmonary embolectomy has a small role to play in major emboli with cardiovascular collapse, if surgery can start within 2 hours and pulmonary angiography is available. Cardiopulmonary by-pass on its own may be life-saving in supporting the circulation while the clot fragments. If cardiac arrest occurs, external cardiac massage should be undertaken as it is sometimes successful and disseminates and fragments the clot in the pulmonary artery.