A system for measuring total body calcium in man using the 40Ca(n, alpha)37 Ar reaction.

A technique to measure total body calcium using the 40Ca(n, alpha)37 Ar reaction has been developed. The technique is based on collecting 37Ar exhaled in the breath following a 10 mrad uniform total body irradiation by 14 MeV neutrons. The 37Ar in the exhaled breath is extracted by selective absorption and its radioactivity is measured inside a low-background proportional detector. The facilities developed include an activation facility providing a +/-2.7% activation uniformity, a closed circuit rebreathing and gas collection system, and a gas purification and counting system. The technique provides a precision of +/-2.4% as determined by repetitive measurements of human volunteers and has an accuracy for determination of total body calcium in grams of +/-5%.     

Modulation of Ca2+-activated K+ currents and Ca2+-dependent action potentials by exocytosis in goldfish bipolar cell terminals

Retinal bipolar cells convey light-evoked potentials from photoreceptors to ganglion cells and mediate the initial stages of visual signal processing. They do not fire Na⁺-dependent action potentials (APs) but the Mb1 class of goldfish bipolar cell exhibits Ca²⁺-dependent APs and regenerative potentials that originate in the axon terminal. I have examined the properties of Ca²⁺-dependent APs in isolated bipolar-cell terminals in goldfish retinal slices. All recorded terminals fired spontaneous or evoked APs at frequencies of up to 15 Hz. When an AP waveform was used as a voltage stimulus, exocytosis was evoked by single APs, maintained throughout AP trains and modulated by AP frequency. Furthermore, feedback inhibition of the Ca²⁺ current ( I _Ca) by released vesicular protons reduced depression of exocytosis during AP trains. In the absence of K⁺ current inhibition, step depolarizations and AP waveforms evoked a rapidly activated outward current that was dependent on Ca²⁺ influx ( I _K(Ca)). I therefore investigated whether proton-mediated feedback inhibition of I _Ca affected the activation of I _K(Ca). A transient inhibition of I _K(Ca) was observed that was dependent on exocytosis, blocked by high-pH extracellular buffer, of similar magnitude to inhibition of I _Ca but occurred with a delay of 2.7 ms. In addition, the amplitude of APs evoked under current clamp was inhibited by the action of vesicular protons released by the APs. Protons released via exocytosis may therefore be a significant modulator of Ca²⁺-dependent currents and regenerative potentials in bipolar-cell terminals.     

The effects of buffer ingestion on metabolic factors related to distance running performance

We examined the effects of sodium bicarbonate (BIC) and sodium citrate (CIT) ingestion on distance running performance. Seven male runners [mean = 61.7 (SEM 1.7) ml · kg^–1 · min^–1] performed three 30-min treadmill runs at the lactate threshold (LT) each followed by a run to exhaustion at 110% of LT. The runs were double-blind and randomly assigned from BIC (0.3 g · kg body mass^–1), CIT (0.5 g · kg body mass^–1) and placebo (PLC, wheat flour, 0.5 g · kg body mass^–1). Venous blood samples were collected at 5, 15 and 25 min during the run and immediately post-exhaustion (POST-EX) and analysed for pH, and the concentrations of lactate ([1a^–]_b) and bicarbonate ([HCO₃ ^– ]). Performance was measured as running time to exhaustion at 110% of LT (TIME-EX). The pH was significantly higher (P 0.05) for the BIC and CIT trials during exercise, but not POST-EX compared to PLC. The [1a^–]_b was significantly higher (P 0.05) for the CIT trial compared to PLC during exercise, and for both CIT and BIC compared to PLC at POST-EX. Blood [HCO₃ ^–] was significantly higher (P 0.05) during exercise for BIC compared to PLC. TIME-EX was not significantly different among treatments: BIC 287 (SEM 47.4) s; CIT 172.8 (SEM 29.7) s; and PLC 222.3 (SEM 39.7) s. Despite the fact that buffer ingestion produced favourable metabolic conditions during 30 min of high intensity steady-state exercise, a significant improvement in the subsequent maximal exercise run to exhaustion did not occur.     

Direct infant UV light exposure is associated with eczema and immune development

1. Download high-res image (389KB)
2. Download full-size image

     

The vascular territories (angiosomes) of the body: experimental study and clinical applications

The blood supply to the skin and underlying tissues was investigated by ink injection studies, dissection, perforator mapping and radiographic analysis of fresh cadavers and isolated limbs. The results were correlated with previous regional studies done in this department. The blood supply is shown to be a continuous three-dimensional network of vessels not only in the skin but in all tissue layers. The anatomical territory of a source artery in the skin and deep tissues was found to correspond in most cases, giving rise to the angiosome concept. Arteries follow closely the connective tissue framework of the body. The primary supply to the skin is by direct cutaneous arteries which vary in calibre, length and density in different regions. This primary supply is reinforced by numerous small indirect vessels, which are "spent" terminal branches of arteries supplying the deep tissues. An average of 374 major perforators was plotted in each subject, revealing that there are still many more potential skin flaps. Our arterial roadmap of the body provides the basis for the logical planning of incisions and flaps. The angiosomes defined the tissues available for composite transfer.     

Autoimmunity to insulin, beta cell dysfunction, and development of insulin-dependent diabetes mellitus

Circulating insulin autoantibodies (INSAAb) were measured in discordant monozygotic twins, first-degree relatives, and other groups at "high risk" for the development of insulin-dependent diabetes mellitus (IDDM), and these results correlated with both islet cell antibody (ICAb) status and beta cell function. INSAAb were positive in 31.6% (12 of 38) ICAb-positive subjects but in only 3.1% (3 of 97) ICAb-negative subjects (X2 = 22.4; P less than 0.001). Elevated levels of INSAAb tended to correlate with younger age and were observed in individuals irrespective of the prevailing degree of their beta cell function. Eight of 15 subjects detected to be INSAAb positive have thus far progressed to clinical IDDM (X2 = 18.3; P less than 0.001). Thus, autoantibodies reactive with the insulin molecule (1) appear to constitute an additional serologic marker of ongoing autoimmunity and development of IDDM, and (2) may reflect heterogeneity in the pathogenesis of IDDM.     

The role of the social worker in provincial psychiatric hospitals: an Ontario study

Confusion still exists about the roles and functions of social workers in the mental health care system. The authors discuss this role ambiguity and its effects. They then present and discuss the findings of a study that explored the current role of the social worker in Ontario psychiatric hospitals with the following objectives: to document social workers' major roles and activities; to assess role satisfaction; to assess involvement in decision making; and to identify major types of therapy used.