High-throughput strategies for the discovery and engineering of enzymes for biocatalysis

Bioprocess and Biosystems Engineering - Innovations in novel enzyme discoveries impact upon a wide range of industries for which biocatalysis and biotransformations represent a great challenge,...     

Cohort and tag-site-specific tag-loss rates in mark–recapture studies: A southern elephant seal cautionary case

Marker-loss is a common feature of mark–recapture studies and important as it may bias parameter estimation. A slight alteration in tag-site of double tagged southern elephant seals (Mirounga leonina), marked at Marion Island from 1983 to 2005 in an ongoing mark–recapture program, had important consequences for tag-loss. We calculated age-specific tag-retention rates and cumulative tag-retention probabilities using a maximum likelihood model selection approach in the software application TAG_LOSS 3.2.0. Under the tag-loss independence assumption, double tag-loss of inner interdigital webbing tags (IIT; 17 cohorts) remained below 1% in the first 5 yr and increased monotonically as seals aged, with higher tag-loss in males. Lifetime cumulative IIT tag-loss was 11.9% for females and 18.4% for males, and equivalent for all cohorts. Changing the tag-site to the outer interdigital webbing (OIT; 6 cohorts) resulted in increased and cohort-dependent tag-loss, although the variation (mean ± 95% CI) in cumulative tag-loss probabilities never exceeded 5.3% between cohorts at similar age. Although different studies may homogenize techniques, we advocate the importance of data set-specific assessment of tag-loss rates to ensure greatest confidence in population parameters obtained from mark–recapture experiments. Permanent marking should be implemented where feasible.     

A new device for the freeze-clamping of tissue samples

Measurement of metabolite concentrations in tissue samples involves the following procedures: Removal of the sample from the animal, temporary arrest of metabolism, extraction (including weighing, homogenization, final fixation, and neutralization) and assay. Rapid temporary fixation following the sampling of tissue is essential to prevent autolytic changes in metabolite concentrations (1,2). The freeze-clamping technique described by Wollenberger et al. (3) meets this requirement as long as the final thickness of the freeze-clamped sample is sufficiently small. For brain tissue the limit seems to be about 2 mm (4).In our laboratory we have made extensive use of the freeze-clamping tongs of Wollenberger et al., especially for small tissue samples freeze-clamped in situ. However, when in situ clamping can not be used when more than 2–3 g of tissue must be sampled, the freeze-clamping press described below has proven very useful.