Imaging Ca2+ concentration changes at the secretory vesicle surface with a recombinant targeted cameleon.

Regulated exocytosis involves the Ca(2+)-triggered fusion of secretory vesicles with the plasma membrane, by activation of vesicle membrane Ca(2+)-binding proteins [1]. The Ca(2+)-binding sites of these proteins are likely to lie within 30 nm of the vesicle surface, a domain in which changes in Ca2+ concentration cannot be resolved by conventional fluorescence microscopy. A fluorescent indicator for Ca2+ called a yellow 'cameleon' (Ycam2) - comprising a fusion between a cyan-emitting mutant of the green fluorescent protein (GFP), calmodulin, the calmodulin-binding peptide M13 and an enhanced yellow-emitting GFP - which is targetable to specific intracellular locations, has been described [2]. Here, we generated a fusion between phogrin, a protein that is localised to secretory granule membranes [3], and Ycam2 (phogrin-Ycam2) to monitor changes in Ca2+ concentration ([Ca2+]) at the secretory vesicle surface ([Ca2+]gd) through alterations in fluorescence resonance energy transfer (FRET) between the linked cyan and yellow fluorescent proteins (CFP and YFP, respectively) in Ycam2. In both neuroendocrine PC12 and MIN6 pancreatic beta cells, apparent resting values of cytosolic [Ca2+] and [Ca2+](gd) were similar throughout the cell. In MIN6 cells following the activation of Ca2+ influx, the minority of vesicles that were within approximately 1 microm of the plasma membrane underwent increases in [Ca2+](gd) that were significantly greater than those experienced by deeper vesicles, and greater than the apparent cytosolic [Ca2+] change. The ability to image both global and compartmentalised [Ca2+] changes with recombinant targeted cameleons should extend the usefulness of these new Ca2+ probes.     

Lethal osteogenesis imperfecta congenita and a 300 base pair gene deletion for an alpha 1(I)-like collagen.

Broad boned lethal osteogenesis imperfecta is a severely crippling disease of unknown cause. By means of recombinant DNA technology a 300 base pair deletion in an alpha 1(I)-like collagen gene was detected in six patients and four complete parent-child groups including patients with this disease. One from each set of the patients'' clinically unaffected parents also carried the deletion, implying that affected patients were genetic compounds. The study suggests that prenatal diagnosis should be possible with 100% accuracy in subjects without the deletion and with 50% accuracy in those who possess it (who would be either heterozygous--normal, or affected with the disease).     

Preregistration house officers in eight English regions: survey of quality of training.

OBJECTIVE--To assess the quality of preregistration house officer training in eight English regions. DESIGN--Postal questionnaire. SETTING--Thames, East Anglian, Mersey, Northern, and Wessex regions. PARTICIPANTS--1670 preregistration house officers. MAIN OUTCOME MEASURES--Education, hours of work, workload, conditions of work, and attitudes to job and medicine as a career. RESULTS--Response rate was 69% (1146 replies). Most house officers had attended induction courses (1036/1129 (92%)); 74% (757/1024) found them satisfactory. The proportions who had never received adequate guidance on how to break bad news and how to control pain were 59% (670/1135) and 56% (634/1136) respectively. There was much variation between regions. Overall, 65% (736/1138) reported confidence in performing cardiopulmonary resuscitation. Most respondents (95% (1089/1142)) worked an on call rota, 3% (36) a partial shift, and 0.6% (seven) a full shift; 19% (202) were on duty for average weekly hours that exceeded the targets for 1 April 1993. House officers had a median of 20 patients under their care and clerked a median of 10 emergency cases, six routine cases, and two day cases a week. Over half (690/1128 (61%)) could not obtain hot food after 8 pm, 20% (223/1095) did not always have clean sheets available in their on call room, and 45% (462/1036) did not consider the protection of staff against violence to be adequate at their hospital. The most important problems with the preregistration year were inappropriate or non-medical tasks (ranked first by 360 respondents), hours of work (359), and pay for out of hours work (167). Overall 57% (646/1125) would encourage a friend to apply for their post, but only 24% (266/1112) would encourage a friend to take up medicine and 44% (494/1112) would discourage the idea. CONCLUSIONS--House officers'' training is deficient in important respects, with inappropriate tasks and heavy clinical workloads impeding the provision of proper education.