Experimental Studies on High-Rate Digestion of Nightsoil

The basic mechanism of nightsoil digestion was investigated, in order to develop a better and faster method of treatment. This is a very important sanitary engineering problem which we have to face in South-East Asia. Some useful experimental results of the thermophilic digestion, and the prethickening and the anaerobic contact process, which seem to be applicable to high-rate nightsoil treatment but have not been applied yet to actual plant design, are reported in this paper

A self-renewing, tissue-engineered vascular graft for arterial reconstruction

ObjectiveVarious tissue-engineered vascular grafts have been studied to overcome the clinical disadvantages of conventional prostheses. Previous tissue-engineered vascular grafts have generally required preoperative cellular manipulation or use of bioreactors to improve performance, and their mechanical properties have been insufficient. We focused on the concept of in situ cellularization and developed a tissue-engineered vascular graft for arterial reconstruction that would facilitate renewal of autologous tissue without any pretreatment.MethodsThe graft comprised an interior of knitted polyglycolic acid compounded with collagen to supply a scaffold for tissue growth and an exterior of woven poly-l-lactic acid for reinforcement. All components were biocompatible and biodegradable, with excellent cellular affinity. The grafts, measuring 10 mm in internal diameter and 30 mm in length, were implanted into porcine aortas, and their utility was evaluated to 12 months after grafting.ResultsAll explants were patent throughout the observation period, with no sign of thrombus formation or aneurysmal change. Presence in the neomedia of endothelialization with proper integrity and parallel accumulation of functioning smooth muscle cells, which responded to vasoreactive agents, was confirmed in an early phase after implantation. Sufficient collagen synthesis and lack of elastin were quantitatively demonstrated. Dynamic assessment and long-term results of the in vivo study indicated adequate durability of the implants.ConclusionThe graft showed morphologic evidence of good in situ cellularization, satisfactory durability to withstand arterial pressure for 12 postoperative months, and the potential to acquire physiologic vasomotor responsiveness. These results suggest that our tissue-engineered vascular graft shows promise as an arterial conduit prosthesis