No abstract

Fasting plasma concentrations of magnesium were measured by neutron activation analysis in 30 nondiabetics and 87 diabetics (55 non-insulin-treated, 32 insulin treated). Plasma concentrations of magnesium were lowest in the insulin treated group (mean 0 84 (SEM 0 01) mmol/l; 2 0 (0 02) mg/100 ml), intermediate in the non-diabetics (mean 0 89 (SEM 0 01) mmol/l; 2 2 (0-02) mg/100 ml), and highest in the non-insulintreated diabetics (mean 0-95 (SEM 0 02) mmol/l; 2 3 (005) mg/100 ml). In all diabetics plasma magnesium concentrations were inversely related to plasma glucose values (rs=-0 33; p <0 01) and in non-insulin-treated patients to plasma insulin concentrations (rs =-0 28; p <0 05), the former confirming previous observations.

The renal and vasopressin (AVP) response to a standard oral water load (20 ml/kg) was examined in a group of water-replete healthy elderly men (n = 6). Two groups, respectively, of water-replete and water-deprived young healthy volunteers acted as controls. After 2 h, the old group had excreted 41 +/- 2.4% (mean +/- SEM) of the water load compared to 100.7 +/- 8.8% in the water-replete young group and 70 +/- 3.8% in the water-deprived young group (P less than 0.01). Similarly, peak diuresis (7.01 +/- 0.48 ml/kg) and peak free-water clearance (5.7 +/- 0.48 ml/min) as determined from hourly sampling in the old group were delayed and significantly less than both young groups (P less than 0.01) (peak diuresis, young water-replete, 10.86 +/- 0.56 ml/kg, young water-deprived, 10.2 +/- 0.64 ml/kg, peak free-water clearance, young water-replete 8.4 +/- 0.72 ml/min, young water-deprived 9.5 +/- 0.88 ml/min). When these indices were adjusted for reduced creatinine clearance (Ccr) in the elderly, there was no significant difference between the young and old groups. Plasma AVP decreased similarly in all three groups following ingestion of water but there was no significant difference in mean plasma AVP between the young and old subjects throughout the study period. We therefore conclude that ability to excrete excess water promptly is impaired in healthy elderly men. This defect is due, at least in part, to an age-related reduction in glomerular filtration rate.

This article explores how beginning teachers develop their professional identities and knowledge. It analyses the stories of four student-teachers as they progressed through their pre-service programme and in their first year as primary teachers. During the three-year programme a range of instruments and a series of interviews were used to collect data on their developing subject and pedagogic content knowledge for teaching science, their teaching experiences, their views of teaching and of themselves as teachers. During the visit in school at the end of their first year as qualified teachers they were observed teaching their own classes and a final interview was conducted. The study examined the interaction between knowledge and identities, the extent to which specific subjects may be salient in their identities as general class teachers, and whether those identities were stable and coherent or shifting and conflicting. The stories extend beyond the four years of the study, drawing on the past and imagining futures, and they are analysed with reference to the concept of trajectories as used in relation to communities of practice by Wenger. Some implications are identified for supporting beginning teachers in their identity work and development of knowledge.

Venous blood was taken at the end of a glucose infusion test in 19 individuals and divided into four aliquots, 3 of which were variably haemolysed by repeated passage through a 23-gauge needle to simulate traumatic venepuncture. Plasma insulin (measured by both a charcoal separation and a double-antibody method), C-peptide, and haemoglobin were measured in each aliquot, and haemolysis was also assessed visibly. A significant loss of immuno-assayable plasma insulin was found in samples with only a trace of visible haemolysis, with up to 90% lost in severely haemolysed samples. Plasma C-peptide was unaffected by haemolysis. This represents an additional advantage for the use of plasma C-peptide in assessing insulin secretion.