Mid-life social participation and physical performance at age 60-64: evidence from the 1946 British Birth Cohort Study.

BACKGROUND: Previous studies linking social activity and disability have been limited by focussing on self-reported physical performance in older adults (>65). We examined whether social participation in mid-life is associated with objective and subjective measures of physical performance in older age. METHODS: Participants of the Medical Research Council National Survey of Health and Development reported their involvement in social activities at ages 43 and 60-64 years; frequency of such involvement was classified into thirds. Physical performance was measured at age 60-64 using: grip strength; standing balance; chair rises; timed get-up-and-go; self-reported physical function from the Short Form-36. Multivariable regression was used to examine longitudinal associations between social participation and each physical performance measure. We also investigated whether change in social participation between 43 and 60-64 was associated with each outcome. RESULTS: In fully adjusted models, higher frequency of social participation at 43 was associated with faster chair rise (1.42 repetitions/min, 95% CI 0.45-2.39) and timed get-up-and-go speed (2.47 cm/s, 95% CI 0.27-4.67) and lower likelihood of self-report limitations (OR of low physical function 0.67, 95% CI 0.50-0.91) at 60-64 compared with low frequency. Better performance in objectively measured outcomes was observed only if higher social participation persisted over time whereas lower odds of self-reported limitations were found in all groups when compared to those with persistently low participation (ORs 0.43-0.56, all P≤0.02). CONCLUSION: Our findings suggest that associations between higher levels of social participation in mid-life and better physical performance exist only if this social participation persists through to older age.

A catastrophic death assemblage and paleoclimatic implications of pliocene seabirds of Florida.

A deposit of fossil seabirds from the late Pliocene of Florida includes more than 130 skeletons of an extinct cormorant that is related phylogenetically to Recent species currently restricted to the eastern north Pacific. Evidence suggests the birds died in a single catastrophic event, perhaps a red tide. The fossil cormorant, along with other extinct seabirds and marine mammals, supports molluscan evidence for cold-water upwelling along the Florida Gulf Coast during the Pliocene. A decline in species richness of marine vertebrates throughout the Pliocene of Florida coincides with cessation of upwelling after emergences of the Panamanian Land Bridge.

Purification of porphobilinogen deaminase from Euglena gracilis and studies of its kinetics.

1. Porphobilinogen deaminase [porphobilinogen ammonia-lyase (polymerizing), EC 4.3.1.8] from Euglena gracilis was purified more than 200-fold. 2. The enzyme has a molecular weight of 41 000 +/- 2000, does not contain a chromophoric prosthetic group, and appears not to require metal ions for activity. 3. The stoicheiometry of the overall reaction at pH 7.4 was shown to be: 4 Porphobilinogen leads to uroporphyrinogen-I + 4 NH4+. This stoicheiometry for porphobilinogen and uroporphyrinogen was also observed over a wide range of pH values. 4. Initial-velocity studies showed a hyperbolic dependence of velocity on substrate concentration, demonstrating the existence of a displacement-type mechanism. 5. Vmax. varied with pH as a typical bell-shaped curve, indicating that two ionizable groups with pK values of 6.1 and 8.9 are important for catalysis. A plot of Vmax./Km against pH showed a single ionization (pK 8.2) to influence binding of substrate.