Physiology of the sphincter of Oddi--the present and the future?--Part 1.

The mechanisms controlling the sphincter of Oddi (SO) have received considerable attention over the past two decades. Progress towards their elucidation has been slow, perhaps because of the sphincter's relative inaccessibility and the different responses of the human "resistor" as compared to the "pumper" observed in several animal models. The list of agents affecting the sphincter grows alarmingly. In this review, divided into two parts, substances have been classified as neurotransmitters, hormones, local factors and pharmacological agents. The first part considers the roles of neurotransmitters. These include (a) vasoactive intestinal polypeptide (VIP) and nitric oxide (NO). Both cause relaxation. A recent model of their complex interrelationships in smooth muscle is described. (b) Substance P (SP) and enkephalins. These produce contractions. The former can act directly. An indirect effect via cholinergic neurones may be the result of SP release from vagal afferents. (c) Catecholamines, which cause contraction or relaxation via activation of alpha- or beta-adrenoreceptors, respectively. In the second part attention is focussed on cholecystokinin (CCK) which normally relaxes the SO via neuronal mechanisms. A CCK-sensitive pathway from sensory duodenal neurones to SO ganglia has been described. Reactive oxygen species are among the local factors discussed. Their description as being "the good, the bad and the ugly" seems merited. Pharmacological agents include NO donors, octreotide and botulinum toxin (BTX). Octreotide induces tachyoddia and may impair biliary flow. BTX has exciting potential in the diagnosis of SO abnormalities and as a therapeutic alternative to sphincterotomy. In both parts of the review current concepts of different aspects of smooth muscle control are presented. In several instances data regarding the SO is lacking. We discuss (a) the role of interstitial cell of Cajal in the control of slow waves, (b) different pathways contributing to tonic and phasic contractions, (c) the 4 levels of neural control, (d) interrelationships of immune and nervous systems, and (e) links between emotional states and gut functions.

The physiology of the biliary tree. Motility of the gallbladder--part 1.

An incomplete picture has emerged of the complex means by which gallbladder motility is controlled under normal and pathophysiological conditions. In the first part of this review an overall account is presented. The mechanisms of cholecystokinin release, its stimulation by dietary factors and peptides elaborated by both pancreas and small intestine are discussed. The inhibition of cholecystokinin release by bile acids and proteases is also described. In the second part attention is focussed on other peptides affecting motility. These include (a) octreotide, effective for treatment of acromegaly, (b) peptide YY, contributing to a "colonic brake', (c) motilin. associated with interdigestive contractions, analogues of which possibly correct gallbladder hypomotility, and (d) substance P and calcitonin gene-related peptide, which facilitate ganglionic transmission after release from extrinsic sensory neurones and alter gallbladder responses to vagal stimulation. The sympathetic nervous system and diabetes mellitus also influence vagal responses. The former, acting presynaptically, may provide a "brake" to prevent vagal overactivity. The latter could cause hypomotility via autonomic neuropathy, although hyperglycaemia, itself, may play a role. The role of nitric oxide, released from neurones also producing vasoactive intestinal peptide is recognized. Both lengthen muscle, the former producing responses without requiring plasma membrane receptors. Gallbladder motility also changes during pregnancy and stone formation. Progesterone and cholesterol can limit G protein actions, thus impairing contractions. Inflammation is associated with abnormal motility. The production of reactive oxygen metabolites, acting directly or releasing prokinetic prostaglandins, may be responsible. It has been proposed that the gastrointestinal tract may be normally in a state of controlled inflammation, primed to react to harmful challenges.

Swallowing-induced cardio-respiratory responses in man.

Swallowing transiently increases heart rate. One of the authors developed pronounced bradycardia while breath holding, particularly after an expiration. The objective, therefore, was to study his cardiac responses during swallowing as pronounced bradycardia developed. When, after a maximum inspiration (supine), the heart rate slowly fell below 50 beats min' well-defined P waves (lead II) disappeared. By swallowing 6 times on command after the P waves disappeared his heart rate increased immediately (68 +/- 1 beats min(-1); n=6). P waves with similar morphology to those pre-swallowing were recorded 0.7 +/- 0.1 s (n=6) after the first swallow. He continued breath holding after swallowing. P waves again disappeared, although at faster heart rates (57 +/- I beats min(-1); n=6). Furthermore, well-defined P waves were observed after the second disappearance at heart rates within the range 30-40 beats min(-1). Small amplitude P waves continued to be recorded from lead I with P wave disappearance in lead II, suggesting a pacemaker shift, although not to the av node. Autonomic nerves can shift the dominant pacemaker within the sa node. The present report indicates that increased vagal tone may be rapidly reversed by swallowing.

Effects of exposure to cotton dust on energy expenditure in the textile industry.

An assessment of energy expenditure has been made in 50 male textile workers and 30 male office cleaners. There was a statistically significant difference (P less than 0.001) in energy expenditure between textile workers and office cleaners amounting to 12 to 16%. While 33.3% of the textile group complained of chest disorders, none of the cleaners had such a complaint. FEV1 and FVC values of the textile workers were significantly lower (P less than 0.01) compared to those of the controls. There were no differences in body weight, lean body mass and socio-economic conditions of the two groups, however, the textile workers were younger and taller than the unexposed group. Exposure to cotton dust and respiratory and ventilatory impairments are suspected of causing a reduction in the energy expenditure of the textile workers.

An evaluation of the Oxylog as a portable device with which to measure oxygen consumption.

The Oxylog, a portable device for measuring oxygen consumption, was evaluated under standard, laboratory conditions and with exercising human subjects. The difference in oxygen partial pressure between room air and a series of test gases measured by the Oxylog showed good agreement with results obtained using a paramagnetic analyser and stable values were obtained for at least 6 h. The measurement of oxygen consumption by the Oxylog was assessed under simulated conditions, with an anaesthetic ventilator, and in exercising human subjects. With a simulated steady-state oxygen consumption there was an initial delay of 2 min before any oxygen consumption was recorded. Subsequent increases in simulated oxygen consumption were detected within one minute. The oxygen consumption of exercising human subjects measured with the Oxylog showed very good agreement with simultaneous measurements obtained using the Douglas bag technique. The application of an appropriate conversion factor allows the individual's energy expenditure to be estimated from the oxygen consumption: in this study a factor of 20.08 kJ per litre oxygen consumption gave the best agreement with the Douglas bag estimate.

Growth velocity in children in rural Khartoum, Sudan.

The results of a mixed cross-sectional and longitudinal anthropometric survey of Sudanese children up to the age of sixteen years are reported. Weight velocity, height velocity, mid arm circumference velocity, and mid arm muscle circumference velocity, and the age at which 50% of females have reached menarche have been calculated. Growth velocities are lower than for English children and the puberty growth spurts occurs about one year later in Sudanese than in English children

A portable physiological data recording/decoding system.

Counting the number of heart beats and footsteps during successive minute periods permits assessment of the physical condition of a subject undertaking planned exercise. We describe the design, and assess the use, of a small, 4 channel, solid state recorder for storing these physiological signals and the rapid retrieval of this data using a portable decoder. The actual number of heart beats and footsteps are counted and stored after each successive minute period. One channel is used to code sequentially the subjects under test, and a further channel is used for event marking. Data are retrieved by linking the recorder to the decoder; entering the required subject's code onto a numeric key board initiates the presentation of data. A LED display and paper print-out provide visual and permanent records.