Pharmaceutical Treatment Options for Myasthenia Gravis Article

Pharmaceutical Treatment Options for Myasthenia Gravis - Article Example The neuromuscular junction (NMJ) has the distinction of being the first site of a defined autoantibody mediated neurological disease, namely myasthenia gravis (MG), which is due to autoantibodies to the acetylcholine receptor (AChR) (Vincent, 2002). Other targets at the NMJ include muscle specific kinase (MuSK) in MG patients without AChR antibodies. About 20% of MG patients with generalized disease in Europe, North America and Japan do not have AChR antibodies. These so called 'seronegative' MG patients can be divided into two groups: those with antibodies to MuSK and those without [AChR/MuSK seronegative MG (SN-MG) (Hoch etal, 2001). In normal neuromuscular transmission depolarization of the presynaptic nerve terminal produces an influx of calcium through voltage-gated calcium channels. Vesicles containing acetylcholine (ACh) then fuse with the presynaptic nerve terminal membrane. After release, ACh interacts with the acetylcholine receptor (AChR) on the muscle endplate surface. This opens the AChR channel, resulting in an influx of cations, largely sodium. Depolarization of the muscle surface produces an excitatory endplate potential, and if the endplate potential is of sufficient amplitude, muscle surface voltage-gated sodium channels are opened. This generates an action potential that eventually results in excitation-contraction coupling and muscle movement. ACh binds transiently to its receptor and then either diffuses from the neuromuscular junction or is hydrolyzed by acetylcholinesterase (AChE), providing a self-limited response to nerve depolarization. In MG, antibodies are directed against the acetylcholine receptors (AChR antibodies). AChR antibodies interfere with neuromuscular transmission through one of three mechanisms- First, some bind to the AChR cholinergic binding site, blocking the binding of ACh. Second, some AChR antibodies cross-link muscle surface AChRs, increasing their rate of internalization into muscle and reducing the numbers of available AChRs. Third, and perhaps most importantly, AChR antibodies that bind complement result in destruction of the muscle endplate, and a more long-lasting loss of AChRs. Drugs like acetylcholinestrase inhibitors nhibits AChE, increasing the amount of ACh available to interact with available AChRs, thus prolonging the action of Ach, and allowing muscle contraction. Pharmacological treatment Acetylcholinesterase inhibitors are the first pharmacological choice in the treatment of MG. Acetylcholinesterase is an acetylcholine-hydrolyzing enzyme which binds the overflowing acetylcholine in the neuromuscular junction, keeping the junction clean from excessive transmitter. Acetylcholinesterase inhibitors bind to the acetylcholinesterase, inhibiting its action. Pyridostigmine is a more recent long-acting reversible acetylcholinesterase inhibitor. Acetylcholinesterase inhibitors increase the amount of available acetylcholine in the neuromuscular junction. This leads to enhanced binding of acetylcholine to the diminished number of AChRs on the myasthenic muscle cell membrane, causing contractility improvement (Millard and Broom field, 1995) When additional pharmacological tre

Scientific Concepts and Methodologies Assignment

Scientific Concepts and Methodologies - Assignment Example The lag phase is described with minimized or no uptake of water after the previous imbibition. The water that is imbibed in the first phase is crucial to the processes of physiology that takes place in the second phase. The third phase is the radical protrusion (Vysotï ¸  sï ¸ ¡kiĭ, Kornilova & Smirnov, 2009). The effect of up taking water is the cell enlargement which is characterized by the cell division. The small root enlargement helps in weakening the walls of cells and breaks through the coat of seed. It is evident, that water plays a crucial factor in the germination phases. Water is among the main environmental factors that affect the seed germination. In some cases, water is a single factor that will limit if or not a seed is going to germinate. In the case of marigolds, a given temperature needs to break the dormancy for the marigolds to start the first stage of taking up water. The seeds of marigolds take in water in three staged, each is characterized by the amount of water absorbed and the impact it will have on the amount that is absorbed and the impact it has on the seed itself. The hypothesis if water is given to the marigold seed, the seed will germinate and later grow compared to the seed having no water was supported. From the observation, only three of the seeds without water grew. In the controlled group 8 of the 10 seeds germinated and later grew. The average growth for the controlled group was 4.37 while the average growth for the experimental group was 0.38. Therefore, given water is needed for a seed to grow. The water is important in chemical reactions since it is photosynthesis raw material. Without water no growth can take place and he plants will lack the energy to carry out chemical reactions. 9 of the planted seeds did not grow at all. 2 from the control group and 7 from the experimental group. It is no surprise that some of the marigold seeds did not germinate from the experimental