Caffeine stimulates amyloid beta-peptide release from beta-amyloid precursor protein-transfected HEK293 cells

Extracellular amyloid beta-peptide (A beta) deposition is a pathological feature of Alzheimer's disease and the aging brain. Intracellular A beta accumulation is observed in the human muscle disease, inclusion body myositis. A beta has been reported to be toxic to neurons through disruption of normal calcium homeostasis. The pathogenic role of A beta in inclusion body myositis is not as clear. Elevation of intracellular calcium following application of calcium ionophore increases the generation of A beta from its precursor protein (betaAPP). A receptor-based mechanism for the increase in A beta production has not been reported to our knowledge. Here, we use caffeine to stimulate ryanodine receptor (RYR)-regulated intracellular calcium release channels and show that internal calcium stores also participate in the genesis of A beta. In cultured HEK293 cells transfected with betaAPP cDNA, caffeine (5-10 mM) significantly increased the release of A beta fourfold compared with control. These actions of caffeine were saturable, modulated by ryanodine, and inhibited by the RYR antagonists ruthenium red and procaine. The calcium reuptake inhibitors thapsigargin and cyclopiazonic acid potentiated caffeine-stimulated A beta release. NH4Cl and monensin, agents that alter acidic gradients in intracellular vesicles, abolished both the caffeine and ionophore effects. Immunocytochemical studies showed some correspondence between the distribution patterns of RYR and cellular betaAPP immunoreactivities. The relevance of these findings to Alzheimer's disease and inclusion body myositis is discussed.     

The Tomlinson report and postgraduate medical education

The postgraduate hospitals of London grew up in the nineteenth century and offered a unique national specialist service. Since then specialist services have developed in undergraduate hospitals throughout Britain as well as in London, but the postgraduate hospitals have nevertheless preserved their high levels of staffing. Although numbers of medical posts in the provinces have grown, this has not been by redistribution of London posts but merely differential growth. The fact identified by Tomlinson--that Londoners are not receiving the most appropriate clinical care--is in fact the strongest argument for changing postgraduate medical education. Such education needs to be rooted first in clinical care, though Tomlinson underestimates the importance to education of such care being sited in a shared environment with strong scientific activity.     

Meat tenderness and the calpain proteolytic system in longissimus muscle of young bulls and steers

The objectives of this study were to examine the effects of castration on the calpain proteinase system (mu-calpain, m-calpain, and calpastatin) activities and meat tenderness. Six each, MARC III bulls and steers were slaughtered at approximately 12 mo of age. Longissimus muscle samples were obtained for determining myofibril fragmentation index, Warner-Bratzler shear force, and sensory panel evaluation at 1, 7, and 14 d postmortem, and mu- and m-calpain and calpastatin activities at 24 h postmortem. Bulls produced leaner carcasses with lower (P < .05) quality grades than did steers. Meat from bulls had higher (P < .05) shear force values than meat from steers; however, sensory panelists were unable (P > .05) to detect differences in tenderness or other sensory traits between bulls and steers. Activities of mu- and m-calpain were not affected (P > .05) by castration; however, calpastatin was higher (P < .05) in muscles from the bull carcasses. Lower (P < .05) myofibril fragmentation index values indicate that less proteolysis occurred in muscle from bulls than in muscle from steers during the first 7 d postmortem. Greater calpastatin 24-h activity may be associated with the increased shear force of meat from bulls.     

Lipid and lipoprotein distributions in children by ethnic group, gender, and geographic location--preliminary findings of the Child and Adolescent Trial for Cardiovascular Health (CATCH)

Male and female isometric strength curves for elbow fixation, shoulder flexion, and wrist supination-pronation are obtained during systematic variation in arm configuration. The shape of a given moment-angle curve is found to be a function of the orientations of joints kinematically coupled to the primary joint. It is also found that female elbow strength curves are shifted toward flexion with respect to male elbow-strength curves, suggesting that the in situ rest length of upper-limb muscles relative to joint angle may be longer for males than for females. Experimental results were contrasted with simulation results obtained using a three-dimensional musculoskeletal model which estimates the relationships between initial joint orientations, muscle tension-length behavior, and joint moments. In most of the cases, simulation results complimented experimental data and provided insights into likely in situ muscle rest lengths and moments arms, especially for the multiarticular biceps brachii muscle. Where inconsistencies exist between simulated and experimental data, subtle biomechanical complexities within the forearm and the shoulder girdle complex are identified that require future investigation.