K+ is the major ion responsible for such changes in ion flux, reflecting changes in various K+ channels. Excitation-contraction
As the uterus becomes essentially denervated during gestation, it is unlikely that any coordinated nervous regulation of the myometrium is centrally orchestrated. Excitation
The excitation-contraction coupling of uterine smooth muscle is also very similar to that of other smooth muscle in general, with intracellular increase in calcium (Ca2+) leading to contraction. Nitric oxide (NO) is particularly effective in relaxing the myometrium and in fact has a lower inhibitory concentration 50% (Ki) in human than guinea pig or non-human primate myometrium. Restoration to resting state
Uterine smooth muscle mechanisms of relaxation differ significantly from those of other human smooth muscles. Removal of Ca2+ after contraction induces relaxation of the smooth muscle, and restores the molecular structure of the sarcoplasmic reticulum for the next contractile stimulus. Measuring uterine contractility ex vivo
Ethically-donated human uterine tissues can be used to measure uterine contractility ex vivo. In these experiments, sections of myometrium are set up in an organ bath system that to measure changes in isometric force production. Following functional checks to ensure the tissue is physiologically active, compounds can be added to the organ bath in increasing concentrations to create a cumulative concentration-response curve (CCRC).A key advantage of measuring uterine contractility ex vivo is the ability to eliminate species differences. For example, while magnesium reduces myometrial contractility in animal studies and in vitro, it does not demonstrate the same effect in clinical studies.
As of November 2007, both the conventional injection and the nasal spray are manufactured using chicken eggs. The European Union also approved Optaflu, a vaccine produced by Novartis using vats of animal cells. This technique is expected to be more scalable and avoid problems with eggs, such as allergic reactions and incompatibility with strains that affect avians like chickens.Influenza vaccines are produced in pathogen-free eggs that are eleven or twelve days old. The top of the egg is disinfected by wiping it with alcohol and then the egg is candled to identify a non-veinous area in the allantoic cavity where a small hole is poked to serve as a pressure release. A second hole is made at the top of the egg, where the influenza virus is injected in the allantoic cavity, past the chorioallantoic membrane. The two holes are then sealed with melted paraffin and the inoculated eggs are incubated for 48 hours at 37 degrees Celsius. During incubation time, the virus replicates and newly replicated viruses are released into the allantoic fluidAfter the 48-hour incubation period, the top of the egg is cracked and the ten milliliters of allantoic fluid is removed, from which about fifteen micrograms of the flu vaccine can be obtained. At this point, the viruses have been weakened or killed and the viral antigen is purified and placed inside vials, syringes, or nasal sprayers. Done on a large-scale, this method is used to produce the flu vaccine for the human population.