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Monoamine Oxidase Inhibitors (MAOIs). The MAOls work in a unique fashion by blocking the activity of an enzyme that degrades each of three key brain transmitters norepinephrine, dopamine, and serotonin. These widespread effects on several brain transmitter systems make the MAOls a potentially very effective class of medications for a variety of disorders. A few small studies have evaluated the usefulness of the MAOls in the treatment of BPD and found them moderately helpful for the impulsivity associated with this illness. Unfortunately, the requirements for strict dietary restrictions due to a risk of hypertensive crisis severely limit the usefulness of MAOls in the treatment of BPD. These restrictions are a particular concern when treating patients who have problems with impulsivity and are therefore likely to have difficulty maintaining the dietary regimen. For this reason, although they may theoretically be helpful, MAOls should only be used to treat BPD after other more easily tolerated medications have been tried and have failed. In the near future, so-called reversible MAOls that appear to avoid the need for diet restrictions may become available. If so, this will allow us to reconsider their use in the treatment of BPD. For more information regarding the use of MAOls, please refer to Chapter 3. 

There is now evidence that the mammalian central nervous system contains several dozen neurotransmitters such as acetylcholine, noradrenaline, dopamine and 5-hydroxytryptamine (5-HT), together with many more co-transmitters, which are mainly small peptides such as met-enkephalin and neuromodulators such as the prostaglandins. It is well established that any one nerve cell may be influenced by more than one of these transmitters at any time. If, for example, the inhibitory amino acids (GABA or glycine) activate a cell membrane then the activity of the membrane will be depressed, whereas if the excitatory amino acid glutamate activates the nerve membrane, activity will be increased. The final response of the nerve cell that receives all this information will thus depend on the balance between the various stimuli that impinge upon it. 

The chemical transmitters may be small molecules— notably acetylcholine, norepinephrine, epinephrine, serotonin, dopamine, or histamine. Acetylcholine and norpeinephrine are the dominant neurotransmitters in the parasympathetic and sympathetic nervous systems, respectively. Dopamine and serotonin are employed primarily in the central nervous system. Neurotransmitters may also be more complex peptides (small proteins) such as substance P, vasopressin, endorphins, and enkephalins. The latter agents are of particular importance to our considerations of opium since they represent the endogenous opiates—agents that exist within the body whose actions are mimicked by exogenous, or outside, agents such as morphine, heroin, codeine, and so on. These neurotransmitters serve to convey information between neurons across the synaptic cleft (the junction where two neurons meet) or at the neuroeffector junction (the site between neuron and an innervated organ such as muscle or secretory gland). 

The nervous system has several properties in common with the endocrine system, which is the other major system for control of body function. These include high-level integration in the brain, the ability to influence processes in distant regions of the body, and extensive use of negative feedback. Both systems use chemicals for the transmission of information. In the nervous system, chemical transmission occurs between nerve cells and between nerve cells and their effector cells. Chemical transmission takes place through the release of small amounts of transmitter substances from the nerve terminals into the synaptic cleft. The transmitter crosses the cleft by diffusion and activates or inhibits the postsynaptic cell by binding to a specialized receptor molecule. In a few cases, retrograde transmission may occur from the postsynaptic cell to the presynaptic neuron terminal. 

Infrared and Raman spectroscopy, coupled with optical microscopy, provide vibrational data that allow us to chemically characterise geochemical sediments and weathered samples with lateral resolutions of 10-20 pm and 1-2 pm respectively. Fourier transform infrared spectroscopy involves the absorption of IR radiation, where the intensity of the beam is measured before and after it enters the sample as a function of the light frequency. Fourier transform infrared is very sensitive, fast and provides good resolution, very small samples can be analysed and information on molecular structure can be obtained. Weak signals can be measured with high precision from, for example, samples that are poor reflectors or transmitters or have low concentrations of active species, which is often the case for geochemical sediments and weathered materials. Samples of unknown... 

Easy integration of sample systems with multiple physical/chemical sensors utilizing modem multi-drop commimication networks. An important aspect of the communication network (NeSSI -bus) is plug-n-play (i.e., self-identification/self-configuration of sensors and actuators) interchangeability. Increased use of small, smart, integrated sampling, sensor, and analyzer transmitters to provide more information about the sample and the process. Validation of representative sample and analysis. 

Studies of the ultrastructure of glomeruli in M. sexta have revealed pre- and postsynaptic profiles, where one pre-synaptic region is commonly associated with several postsynaptic (Tolbert and Hildebrand 1981). Pre-synaptic profiles are not only present in terminals of primary axons. Identification of second-order neurons filled with horseradish peroxidase, have shown that local interneurons also possess pre-synaptic profiles. Similar indications that information is not only received by second-order neurons but also transmitted, were previously provided by degenerating studies in Periplaneta americana and Calli-phora erythrocephala (Boeckh et al., 1970). One of three types of pre-synaptic profiles is most common in M. sexta and seems to be the predominant type in the primary axon terminals (Tolbert and Hildebrand, 1981). These are characterized by their numerous small roimd and clear vesicles, resembling cholinergic terminals in vertebrates, that use acetylcholine as a transmitter (Sanes et al., 1977). 

This is the interval that data can be reported in or captured. The smaller the interval, the greater the information available for processing, decon-volution, etc Many instruments allow the user to switch from transmittance to reflectance The optical component quality determines the overall quaUty of measurements made on an instrument. Poor-quality optics result in high stray light, small dynamic range, higher noise, poor photometric accuracy and reproducibility, poor wavelength accuracy and reproducibility, etc... 

Let us recall the mle of thumb given at the start of this chapter (i.e., a strong band in a 10-pm film of a pure material has a typical absorbance of about 1 AU). Furthermore, we will assume that the strongest band in the spectmm of the analyte must have an absorbance of at least 0.001 AU (1 mAU) for the analyte to be identified above the noise level, interference by atmospheric water vapor, and small variations of the baseline. These constraints imply that the thickness of a sample containing 1 ppm of the analyte must be 1 cm if a trace component is to yield a recognizable spectmm. However, the transmittance of most samples that are 1 cm thick is well below 0.1% in those spectral regions where chemically useful information is to be found (3100 to 2700 and 1800 to 400 cm ). Thus, windows in the spectmm of the matrix material must be found where at least one characteristic band of analyte absorbs. An example of just such a case is found in the determination of antioxidants in polyolefins. Many polyolefins have weak absorption between... 

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