Changes in chemosensitivity of developing chick muscle fibres in relation to endplate formation

1. The sensitivity to acetylcholine (ACh) of the fast posterior latissimus dorsi (PLD) and slow anterior latissimus dorsi (ALD) during embryonic development was studied and compared. The sensitivities were expressed as a ratio of the maximal tetanic tension and tension developed in response to ACh. 2. Up to the 17th day of incubation both muscles are sensitive to ACh to a similar extent; at the 18th day the sensitivity of the PLD muscle decreases and continues to do so until hatching and thereafter. 3. Since the decrease in sensitivity of PLD muscles takes place a few days after innervation, it is suggested that this is caused by activity of the motor nerve. To test this curare (dTc) and hemicholinium (HC-3), drugs that interfere with neuromuscular transmission, were injected into the yolk sac of the embryos when nervemuscle connections are usually established. In the curare and HC-3 treated embryos the desensitization of the PLD muscles did not take place. 4. The distribution of endplates on PLD muscles from drug treated 20-21 day old embryos was compared to that of untreated controls. Whereas control PLD muscles have only one band of endplates, muscles from curarized embryos and HC-3 treated embryos have several bands of endplates, and many muscle fibres with multiple innervation were found. 5. It is suggested that nerve fibres which make connections with PLD muscle fibres bring about a decline in chemosensitivity by releasing more transmitter, and thereby prevent further nerve muscle connections from being made along the same muscle fibre.     

Evaluation procedures for membership of the Royal New Zealand College of General Practitioners

Membership of the Royal New Zealand College of General Practitioners is by examination. The criteria for membership and form of the examination have changed over the years. The latest examination includes two parts, part one including a multiple choice questionnaire and a simulated patient interview. Experienced practitioners can be excused this part. Part two includes a clinical diary and a visit to the practice during which the examiner watches consultations for half a day.     

Properties of implanted electrodes for functional electrical stimulation

Implanted wire electrodes are increasingly being used for the functional electrical stimulation of muscles in partially paralysed patients, yet many of their basic characteristics are poorly understood. In this study we investigated the selectivity, recruitment characteristics and range of control of several types of electrode in triceps surae and plantaris muscles of anaesthetized cats. We found that nerve cuffs are more efficient and selective (i.e., cause less stimulus spread to surrounding muscles) than intramuscular electrodes. Bipolar intramuscular stimulation was more efficient and selective than monopolar stimulation, but only if the nerve entry point was between the electrodes. Monopolar electrodes are efficient and selective if located close to the nerve entry point, but their performance declines with distance from it. Nonetheless, for a variety of reasons monopolar stimulation provides the best compromise in many current applications. Short duration pulses offer the best efficiency (least charge per pulse to elicit force) but high peak currents, increasing the risk of electrode corrosion and tissue damage. Electrode size has little effect on recruitment and should therefore be maximised because this minimises current density.     

Laboratory infection of primates with Ascaris suum to provide a model of allergic bronchoconstriction

Wild-caught non-human primates are naturally sensitive to Ascaris antigen and provide a useful model for studying atopic asthma. The present study was carried out to determine the effect of experimentally infecting home-bred macaques with the nematode Ascaris suum and hence provide an alternative for the naturally occurring model. Following oral infection with the parasite the animals developed a blood eosinophilia and specific antibodies to purified Ascaris antigen. These antibodies appeared to be of the IgE class as they could be detected by a radiometric assay using a radiolabelled antibody to human IgE. However, on further investigation, using the passive cutaneous anaphylaxis test, two classes of antibody were found, a heat labile (56 degrees C) and a heat stable antibody. Lung lavage cells taken from monkeys infected with Ascaris suum were shown to include cells morphologically characteristic of mast cells and released histamine when challenged in vitro with Ascaris antigen. Hence this model of immediate hypersensitivity provides a simple alternative to the less accessible natural model.     

Intra-articular IL-10 gene transfer regulates the expression of collagen-induced arthritis (CIA) in the knee and ipsilateral paw

We studied the effects of local IL-10 application, introduced by a recombinant human type 5 adenovirus vector, in the mouse knee joint during the early phase of CIA. One intra-articular injection with the IL-10-expressing virus (Ad5E1mIL-10) caused substantial over-expression of IL-10 in the mouse knee joint, using virus dosages which did not induce distracting inflammation. High expression of IL-10 was noted for a few days, being maximal at day 1. One intra-articular injection of Ad5E1mIL-10 in the knee joints of collagen type II (CII)-immunized mice, before onset of CIA was noted, reduced the incidence of collagen arthritis in that knee. Of high interest, the protective effect of local IL-10 expression by Ad5E1mIL-10 was not restricted to the knee joint alone. The arthritis incidence in the ipsilateral paw was highly suppressed. In contrast, local IL-10 over-expression was not effective when treatment was started after onset of CIA. Further analysis in the acute streptococcal cell wall-induced arthritis model revealed that local IL-10 over-expression markedly suppressed the production of tumour necrosis factor-alpha (TNF-alpha) and IL-1alpha, but had no significant effect on IL-1beta and IL-12 production in the inflamed synovium. These data indicate that local over-expression of IL-10 in the knee joint of mice regulates the expression of collagen arthritis, probably through down-regulation of TNF-alpha.     

Duplication 2 (q11.2-q21): a previously unreported abnormality

A 7 year old boy is described with moderate learning disability, facial dysmorphism, and a de novo duplication of chromosome 2 (q11.2-q21). There are few published reports of proximal 2q duplication, and none reporting direct de novo duplication for this exact region.     

Calibration and performance of a small animal gradient layer calorimeter box

Calorimetry, using the gradient layer technique, has become well established in the study of energy metabolism. The use of a commercially constructed gradient layer box within a calorimetry system designed to measure directly and indirectly the metabolic sequelae of thermal injury in rats, is described. Variations in the signal output were discovered. These were found to be dependent upon:

1. stability of the ambient temperature
2. stability of the gradient layer box water jacket temperature
3. position and size of the calibrating heat source.

Calibration with heat sources which simulate the heat emission from a rat, established that a measurement accuracy of ±2% can be achieved by controlling (a) and (b)