By Y. Gorn. Olin College of Engineering. 2017.

These in- the most common means of parenteral drug administra- clude (1) capillary permeability dramamine 50 mg without prescription, (2) blood flow–tissue tion. Drug absorption (6) the permeability characteristics of specific tissue from intramuscular and subcutaneous sites depends on membranes. The rate of Advantages of the intramuscular and subcutaneous passage of drugs across capillary walls can be influenced routes include an increased reliability and precision in by agents that affect capillary permeability (e. Pain, tender- ness, local tissue necrosis (primarily with highly alkaline injections), microbial contamination, and nerve damage AVAILABLE DISTRIBUTION VOLUME may be associated with these forms of parenteral ad- The total volume of the fluid compartments of the body ministration. These compartments include plasma Intravenous Administration water (approximately 10 L), interstitial fluid (10 L), and the intracellular fluid (20 L). Total extracellular water is Intravenous drug administration ensures immediate the sum of the plasma and the interstitial water. Factors pharmacological response; problems of absorption are such as sex, age, edema, pregnancy, and body fat can in- circumvented because the entire quantity of drug enters fluence the volume of these various compartments. The pharmacokinetic concept of vol- A serious disadvantage of intravenous drug admin- ume of distribution (a derived parameter that relates istration becomes clearly apparent when an overdose the amount of drug in the body to the plasma concen- is inadvertently given: Neither can the drug be re- tration) is discussed more fully in Chapter 5. Other disadvan- tages include the possibilities of embolism (particu- larly if an insoluble drug is given), introduction of BINDING OF DRUGS TO PLASMA bacteria, and when this route is used for prolonged pe- PROTEINS riods, subcutaneous tissue infiltration. The possible in- troduction of the human immunodeficiency virus Most drugs found in the vascular compartment are (HIV) is a well-known consequence of intravenous bound reversibly with one or more of the macromole- drug administration in addicts who use contaminated cules in plasma. Many highly al- ion and in dynamic equilibrium, according to the law of bumin-bound drugs are poorly soluble in water, and for mass action. Since only the unbound (or free) drug dif- such drugs, binding to hydrophobic sites on albumin is fuses through the capillary walls, extensive binding may often important. The magnitude of of an acidic drug are bound per albumin molecule, this decrease is directly proportional to the fraction of whereas basic, positively charged drugs are more drug bound to plasma protein. As drug nonspecific; that is, many drugs may interact with the dosage increases, eventually the binding capacity of the same binding site. A drug with a higher affinity may dis- protein becomes saturated and any additional drug will place a drug with weaker affinity. However, in practice, changes in protein bind- culation, thereby slowing the rate of transfer across the ing result in clinically significant effects for only a lim- capillary.

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A tentative hypothesis would be that a dual mechanism operates at the spinal level dramamine 50 mg lowest price. The subthreshold preparation to move, reflected by the increased corticospinal tract activity, would be paralleled by an inhibitory influence for suppressing the overt movement. They showed that, during the waiting period where the monkey is ready to move, spinal inter- neurons are activated, hence indicating that the spinal motor network is being primed by the descending cortico-motoneuronal input. Because the overt movement was suppressed during this period, Prut and Fetz hypothesized a superimposed global inhibition, possibly originating in the premotor cortex, and propagating to the spinal cord, parallel to the excitatory input. This hypothesis would account for both the increased motoneuron excitability and the block of muscular activity during action representation. Its empirical basis accumulated from experiments in cognitive neuroscience in the past two decades. One of the most influential results showed that visual mental images rely on acti- vation of the early stages of information processing of the visual system. The primary visual cortex (V1) is consistently involved in visual mental imagery,52,53 with an additional selective involvement of the inferotemporal cortex during imagery of visual objects and of the occipitoparietal cortex in visual spatial imagery. The explanation put forward for an activation of low-level processing areas during a high-level cognitive activity is that activation of topographically organized areas, such as V1, is needed for replacing the image within a spatial frame of reference. Higher-order areas, because they lack topographical organization, would not be able, by themselves, to achieve this task. In other words, the processing of visual imagery would have to follow the same processing track as visual perception for giving an image its spatial layout, a process that requires the participation of V1. The definition we gave at the beginning of this paper for represented actions is that they correspond to covert, quasi-executed actions, a definition that accounts for many of the properties of action representations that have been described here. Thus, by drawing a parallel with perceptual representations such as visual mental imagery, we come to the proposition that, if a represented action is a simulated action, then it should involve the mechanisms that normally participate in motor execution.

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Translocation—The transfer of one part of a chro- Lymphoma—A malignant tumor of the lymph nodes discount dramamine 50 mg amex. A balanced translocation occurs when pieces cell not destined to become a sperm or egg—dupli- from two different chromosomes exchange places cates its chromosomes and divides to produce two without loss or gain of any chromosome material. An unbalanced translocation involves the unequal loss or gain of genetic information between two Mutation—A permanent change in the genetic chromosomes. The Sometimes this translocation results in the transfer of a resulting oncogene produces an unregulated protein proto-oncogene next to a gene involved in the immune that is involved in stimulating uncontrolled cell prolif- system. The first discovered fusion oncogene resulted the immune system gene and as a result becomes dereg- from a Philadelphia chromosome translocation. One example of this mechanism is the transfer of type of translocation is found in the leukemia cells of the c-myc proto-oncogene from its normal location on greater than 95% of patients with a chronic form of chromosome 8 to a location near an immune system gene leukemia. It is not GALE ENCYCLOPEDIA OF GENETIC DISORDERS 835 known how this protein contributes to the formation of Oncogenes as targets for cancer treatment cancer cells. The discovery of oncogenes approximately 20 Some oncogenes result when multiple copies of a years ago has played an important role in developing an proto-oncogene are created (gene amplification). Oncogenes promise to play an amplification often results in hundreds of copies of a even greater role in the development of improved can- gene, which results in increased production of proteins cer therapies since oncogenes may be important targets and increased cell growth. Multiple copies of proto-onco- for drugs that are used for the treatment of cancer. Sometimes amplified goal of these therapies is to selectively destroy cancer genes form separate chromosomes called double minute cells while leaving normal cells intact. Many anti-can- chromosomes and sometimes they are found within nor- cer therapies currently under development are designed mal chromosomes. Other therapies hope to trigger specific oncogenes to cause programmed cell In most cases, oncogenes result from changes in death in cancer cells.

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After the tube is in the stomach buy generic dramamine 50 mg, inflate the balloon with 5–10 mL of air, inject 2–3 mL of mer- cury into the balloon, and then aspirate the air. Feeding Tubes Virtually any NG tube can be used as a feeding tube, but it is preferable to place a spe- cially designed nasoduodenal feeding tube. These are of smaller diameter (usually 8 French) and are more pliable and comfortable for the patient. Weighted tips tend to travel into the duodenum, which helps prevent regurgitation and aspiration. Most are supplied with stylets that facilitate positioning, especially if fluoroscopic guidance is needed. Always verify the position of the feeding tube with an x-ray prior to starting tube feeding. Commonly used tubes include the mercury-weighted varieties (Keogh tube, Duo-Tube, Dobbhoff, Entriflex), the tungsten-weighted (Vivonex tube), and the unweighted pediatric feeding tubes. Sengstaken–Blakemore tube:A triple-lumen tube used exclusively for the con- trol of bleeding esophageal varices by tamponade. One lumen is for gastric aspira- tion, one is for the gastric balloon, and the third is for the esophageal balloon. Other types of tubes used to control esophageal bleeding include the Linton and Minnesota tubes. Ewald tube:An orogastric tube used almost exclusively for gastric evacuation of blood or drug overdose. Dennis, Baker, Leonard tubes: These are used for intraoperative decompression of the bowel and are manually passed into the bowel at the time of laparotomy.