Influence of suture tension to the tearing characteristics of the soft tissues: an in vitro experiment

OBJECTIVES: To evaluate the influence of flap tension on the tearing characteristics of mucosal tissue samples in relation to various suture and needle characteristics. MATERIAL AND METHODS: Lining and masticatory mucosal tissue samples obtained from pig jaws were prepared for in vitro testing. Tension tearing diagrams of 60 experiments were traced for 3-0, 5-0 and 7-0 sutures with applied forces up to 20 N. In the second part, the same experiments were repeated with 100 diagrams to test the influence of needle characteristics with 5-0 and 6-0 sutures using only gingival tissue samples. RESULTS: 3-0 sutures mainly lead to tissue breakage at an average of 13.4 N. In contrast, 7-0 sutures only resulted in breakage of the thread at a mean applied force of 3.7 N. With 5-0 sutures, both events occurred at random at a mean force of 14.6 N. Irrespective of the needle characteristics, the mean breaking force for gingival samples with 5-0 and 6-0 sutures was approximately 10 N. CONCLUSIONS: Tissue trauma may be reduced by choosing finer suture diameters, because thinner (6-0, 7-0) sutures lead to thread breakage rather than tissue breakage.

Habitat fragmentation and adaptation: a reciprocal replant-transplant experiment among 15 populations of Lychnis flos-cuculi

1. Habitat fragmentation and variation in habitat quality can both affect plant performance, but their effects have rarely been studied in combination. We thus examined plant performance in response to differences in habitat quality for a species subject to habitat fragmentation, the common but declining perennial herb Lychnis flos-cuculi. 2. We reciprocally transplanted plants between 15 fen grasslands in north-east Switzerland and recorded plant performance for 4 years. 3. Variation between the 15 target sites was the most important factor and affected all measures of plant performance in all years. This demonstrates the importance of plastic responses to habitat quality for plant performance. 4. Plants from smaller populations produced fewer rosettes than plants from larger populations in the first year of the replant-transplant experiment. 5. Plant performance decreased with increasing ecological difference between grassland of origin and target grassland, indicating adaptation to ecological conditions. In contrast, plant performance was not influenced by microsatellite distance and hardly by geographic distance between grassland of origin and target grassland. 6. Plants originating from larger populations were better able to cope with larger ecological differences between transplantation site and site of origin. 7. Synthesis: In addition to the direct effects of target grasslands, both habitat fragmentation, through reduced population size, and adaptation to habitats of different quality, contributed to the performance of L. flos-cuculi. This underlines that habitat fragmentation also affects species that are still common. Moreover, it suggests that restoration projects involving L. flos-cuculi should use plant material from large populations living in habitats similar to the restoration site. Finally, our results bring into question whether plants in small habitat remnants will be able to cope with future environmental change.