Journal of Bioengineering & Biomedical Science

The existence of isoform diversity among antioxidant enzymes contributes to the spatial and temporal fine tuning of cellular responses. In plants heme binding ascorbate peroxidase (APX) (EC, 1.11.1.11) presents a crucial line of defense against reactive oxygen species. The present study aims to provide a comparative view of the functional attributes of major isoforms of APX in plants species. A total of 64 protein sequences of APX were subjected to homology search, multiple sequence alignment, phylogenetic tree construction, and motif analysis. The phylogenetic tree constructed revealed different clusters based on heme binding APX in respect of dicot and monocot plants such as different source of plant species represented by Oryza sativa, Arabidopsis thaliana, Sorghum bicolor, Zea mays, Ricinus communis, Populus trichocarpa, Vitis vinifera, and Selaginella moellendorffii. The multiple sequence alignment of these APX protein sequences from different plants showed conserved regions at different stretches with maximum homology in amino acid residues. The motif analysis revealed a conserved peroxidase domain uniformly observed in all APX irrespective of variable plant species suggesting its possible role in structural and enzymatic functions. The signature amino acids sequence of VFYQMGLSDKDIVALSGGHTLGRCH, NNGLHIAIRLCQPIKEQFPIITYADFYQLAGVVAVEVTGGPTIPMHPGRV and LFEDPSFRPYVEKYAKDQDAFFKDYAEAHMKLSELGF, related with the plant heme binding peroxidase as well as chloroplastic and cytosolic peroxidase signature was frequently observed and seemed to be related with the structure and enzymatic function in all APX protein sequences. The findings of the present study may be useful for designing degenerate primers or probes specific for APX and possibly presents the first line of defense amongst all the APX isoforms involved in the cellular antioxidant defense pathway, during exposure to abiotic stresses.

Complications of limb lengthening include stress on soft tissue, premature consolidation, and bone non-union. This study reports on the development and testing of instrumentation that continually measures distraction forces in rabbits with the aim of relating the forces developed to bone growth and muscle physiology. A full bridge strain gage resistor set mounted to a unilateral distractor measured distraction force and stored the data on a self-contained logger attached to a jacket worn by the rabbit. Two rabbits underwent limb lengthening on one hind leg. Lengthening was set at 0.5 mm/ day, twice per day for a total of 12 mm. Tibialis anterior muscle and proximal and distal tibial growth plates from the operated and control legs were harvested after euthanasia for histomorphometric analysis. Radiographs were taken periodically throughout lengthening. Force data show characteristic overall increase in force. Force steadily decays after each lengthening. Peak forces appear to correlate with time between lengthenings. Histologic data show that the operated leg had an increased preponderance of type I muscle fibers, a decrease in type-I and type-II muscle fiber diameters, and a decrease in endogenous bone growth at the distal growth plate. Histomorphometric analysis showed that the lengthening paradigm employed altered distal bone growth and muscle fiber physiology during lengthening.