Artificial heart valve was later changed to use silicone-coated material. The first implantation of mechanical heart valve to human was performed by Dr. Hufnagel on 11 September 1952, using the valve that he developed. This event accelerated the development of other artificial heart valves. Artificial heart valve An artificial heart valve is a device implanted in the heart of a patient with valvular heart disease. When one of the four heart valves malfunctions, the medical choice may be to replace the natural valve with an artificial valve. This requires open-heart surgery. Valves are integral to the normal physiological functioning of the human heart.
Human artificial chromosome artificial chromosome vectors. The first is to create a small minichromosome by altering a natural human chromosome. This is accomplished by truncating the natural chromosome, followed by the introduction of unique genetic material via the Cre-Lox system of recombination. The second method involves the literal creation of a novel chromosome "de novo". Progress regarding "de novo" HAC formation has been limited, as many large genomic fragments will not successfully integrate into "de novo" vectors. Another factor limiting "de novo" vector formation is limited knowledge of what elements are required for construction, specifically centromeric sequences. A 2009 study has shown additional