By I. Connor. Stevenson University. 2018.
Dideoxynucleotides lack a 3 -hydroxyl group (in addition to lacking the 2 hydroxyl group normally absent from DNA deoxynucleotides) cheap 20 mg forzest mastercard erectile dysfunction high blood pressure. Thus buy cheap forzest 20 mg online erectile dysfunction protocol book pdf, once they are incorporated into the growing chain, the next nucleotide cannot add, and poly- Probe hybridized merization is terminated. In this procedure, only one of the four dideoxynucleotides to DNA (ddATP, ddTTP, ddGTP, or ddCTP) is added to a tube containing all four normal deoxynucleotides, DNA polymerase, a primer, and the template strand for the DNA that is being sequenced (Fig. As DNA polymerase catalyzes the sequential addition of complementary bases to the 3’ end, the dideoxynubleotide competes with its corresponding normal nucleotide for insertion. Whenever the dideoxynu- Perform autoradiography cleotide is incorporated, further polymerization of the strand cannot occur, and syn- thesis is terminated. Some of the chains will terminate at each of the locations in the template strand that is complementary to the dideoxnucleotide. Consider, for exam- ple, a growing polynucleotide strand in which adenine (A) should add at positions Exposed areas of x-ray film 10, 15, and 17. Competition between ddATP and dATP for each position results in some chains terminating at position 10, some at 15, and some at 17. Thus, DNA strands of varying lengths are produced from a template. The shortest strands are closest to the 5 -end of the growing DNA strand because the strand grows in a 5 to 3 direction. Identification of bacterial colonies containing specific DNA sequences. The Four separate reactions are performed, each with only one of the dideoxynu- autoradiogram can be used to identify bacterial cleotides present (ddATP, ddTTP, ddGTP, ddCTP) plus a complete mixture of nor- colonies on the original agar plate that contain mal nucleotides (see Fig. In each tube, some strands are terminated when- the desired DNA sequence. Note that an orien- ever the complementary base for that dideoxynucleotide is encountered. If these tation marker is placed on the nitrocellulose strands are subjected to gel electrophoresis, the sequence 5 S3 of the DNA strand and the agar plate so the results of the autora- complementary to the template can be determined by “reading” from the bottom to diogram can be properly aligned with the orig- the top of the gel, that is, by noting the lanes (A, G, C, or T) in which bands appear, inal plate of bacteria. Western blots are one of the tests Ivy Sharer is being treated with didanosine. This drug is a purine nucleoside for the AIDS virus. Viral proteins in composed of the base hypoxanthine linked to dideoxyribose. In cells, didano- the blood are detected by antibod- sine is phosphorylated to form a nucleotide that adds to growing DNA strands. Tests performed on Ivy Sharer’s friend Because dideoxynucleotides lack both 2 - and 3 -hydroxyl groups, DNA syn- showed that he was HIV positive. Reverse transcriptase has a higher affinity for the dideoxynu- however, he has not yet developed the cleotides than does the cellular DNA polymerase, so the use of this drug will affect symptoms of AIDS. CHAPTER 17 / USE OF RECOMBINANT DNA TECHNIQUES IN MEDICINE 303 In the early studies on cystic fibrosis, DNA sequencing was used to determine Southern Northern Western the type of defect in patients. Buccal cells were obtained from washes of the mucous membranes of the mouth, DNA isolated from these cells was amplified Gel electrophoresis by PCR, and DNA sequencing of the CF gene was performed. A sequencing gel for the region in which the normal gene differs from the mutant gene is shown below. DNA RNA Protein Normal Mutant G C 16 15 14 13 Transfer to paper 12 (bands not visible) 11 10 9 8 7 6 5 Add probe to 4 visualize bands 3 2 DNA DNA Antibody 1 G What is the difference between the normal and the mutant CF gene sequence shown on the gel, and what effect would this difference have on the protein produced from this gene? For Southern blots, DNA molecules are To study genes or other DNA sequences, adequate quantities of material must be separated by electrophoresis, denatured, trans- ferred to nitrocellulose paper (by “blotting”), obtained. It is often difficult to isolate significant quantities of DNA from the orig- and hybridized with a DNA probe. For example, an individual cannot usually afford to part with enough Northern blots, RNA is electrophoresed and tissue to provide the amount of DNA required for clinical testing. Therefore, the treated similarly except that alkali is not used. CLONING OF DNA blots, proteins are electrophoresed, transferred to nitrocellulose, and probed with a specific The first technique developed for amplifying the quantity of DNA is known as antibody. The DNA that you want amplified (the “foreign” DNA) is attached to a vector (a carrier DNA), which is introduced into a host cell that makes multiple copies of the DNA. The foreign DNA and the vector DNA are usually cleaved with the same restriction enzyme, which produces complementary sticky ends in both DNAs. Base pairs form between the complementary single-stranded regions, and DNA ligase joins the mol- A genomic “library” in molecular ecules to produce a chimera, or recombinant DNA. As the host cells divide, they biologists’ terms is a set of host replicate their own DNA, and they also replicate the DNA of the vector, which cells that collectively contain all of the DNA sequences from the genome of includes the foreign DNA. A cDNA library is a set of If the host cells are bacteria, commonly used vectors are bacteriophage (viruses host cells that collectively contain all the that infect bacteria), plasmids (extrachromosomal pieces of circular DNA that are DNA sequences produced by reverse tran- taken up by bacteria), or cosmids (plasmids that contain DNA sequences from the scriptase from the mRNA obtained from lambda phage).
The role of the thalamus is to sort name means “bridge cheap 20 mg forzest amex erectile dysfunction medication cialis. Certain reflex (invol- helps to maintain homeostasis by controlling body temper- untary) actions buy forzest 20 mg without prescription impotence remedy, such as some of those regulating respira- ature, water balance, sleep, appetite, and some emotions, tion, are integrated in the pons. Both the sympathetic and VIII originate from the pons. The hypothalamus thus influences the heart- beat, the contraction and relaxation of blood vessels, hor- The medulla oblongata of the brain stem is located be- mone secretion, and other vital body functions. It ap- pears white externally because, like the pons, it contains Checkpoint 10-6 What are the two main portions of the dien- many myelinated nerve fibers. Internally, it contains col- cephalon and what do they do? Among these are vital centers, such as the following: The Limbic System ◗ The respiratory center controls the muscles of respira- Along the border between the cerebrum and the dien- tion in response to chemical and other stimuli. This ◗ The cardiac center helps regulate the rate and force of the heartbeat. It in- ◗ The vasomotor (vas-o-MO-tor) center regulates the cludes the hippocampus (shaped like a sea horse), located contraction of smooth muscle in the blood vessel walls under the lateral ventricles, which functions in learning and thus controls blood flow and blood pressure. It also includes regions that stimulate the reticular formation, a network The ascending sensory fibers that carry messages that extends along the brain stem and governs wakeful- through the spinal cord up to the brain travel through the ness and sleep. The limbic system thus links the conscious medulla, as do descending motor fibers. These groups of functions of the cerebral cortex and the automatic func- fibers form tracts (bundles) and are grouped together ac- tions of the brain stem. THE NERVOUS SYSTEM: THE BRAIN AND CRANIAL NERVES 211 The motor fibers from the motor cortex of the cerebral ◗ The Cerebellum hemispheres extend down through the medulla, and most of them cross from one side to the other (decussate) while The cerebellum is made up of three parts: the middle por- going through this part of the brain. The crossing of motor tion (vermis) and two lateral hemispheres, the left and fibers in the medulla results in contralateral control—the right (Fig. Like the cerebral hemispheres, the cere- right cerebral hemisphere controls muscles in the left side bellum has an outer area of gray matter and an inner por- of the body and the left cerebral hemisphere controls mus- tion that is largely white matter. However, the white mat- cles in the right side of the body, a characteristic termed ter is distributed in a treelike pattern. The functions of the contralateral (opposite side) control. The last four pairs of cranial nerves (IX through XII) orderly function. Disease of the cerebellum causes mus- are connected with the medulla. Messages Checkpoint 10-7 What are the three subdivisions of the brain from the internal ear and from sensory receptors in ten- stem? The three parts of the brain stem (midbrain, pons, and medulla oblongata) are also labeled. Philadel- phia: Lippincott Williams & Wilkins, 1998. C, Courtesy of Newport Diagnostic Center, Newport Beach, CA. Anatomic lesions, such as tu- slightly tensed and ready to produce changes in position mors or scar tissue accumulations, are readily seen. Some of the imaging techniques used to study the brain are described in Box 1-2, Medical Imaging: Seeing Without The Electroencephalograph Making a Cut, in Chapter 1. These techniques include: The interactions of the brain’s billions of nerve cells give ◗ CT (computed tomography) scan, which provides pho- rise to measurable electric currents. These may be tographs of the bone, soft tissue, and cavities of the recorded using an instrument called the electroen- Alpha waves- Petit mal Normal, relaxed epilepsy adult Beta waves- Psychomotor State of epilepsy excitement, intense concentration Subdural hematoma Theta waves- Barbiturate Children poisoning Delta waves- Cerebral Deep sleep embolism (blood clot) A 1 second B 1 second Figure 10-13 Electroencephalography. THE NERVOUS SYSTEM: THE BRAIN AND CRANIAL NERVES 213 cephalograph (e-lek-tro-en-SEF-ah-lo-graf). In cases of bacterial meningitis, placed on the head pick up the electrical signals produced early treatment with antibiotics can have good results. These signals are then amplified treated cases have a high death rate. Vaccines are available and recorded to produce the tracings, or brain waves, of against some of the bacteria that cause meningitis. Inflammation of the brain is termed encephalitis (en- The electroencephalograph is used to study sleep pat- sef-ah-LI-tis), based on the scientific name for the brain, terns, to diagnose disease, such as epilepsy, to locate tu- which is encephalon. Infectious agents that cause en- mors, to study the effects of drugs, and to determine brain cephalitis include poliovirus, rabies virus, HIV (the cause death.
Children and pregnant women have a high rate of pro- “Little TV tonight generic forzest 20mg online erectile dysfunction drugs buy. Histidine is essential in the diet of the adult in (tryptophan) PM (phenyl- alanine-methion- very small quantities because adults efficiently recycle histidine forzest 20mg free shipping impotence reasons and treatment. Tyrosine and cysteine are considered conditionally essential. Tyrosine is synthesized from phenylalanine, and it is required in the diet if phenylalanine intake is inadequate, or if an individual is congenitally deficient in an enzyme required to convert phenylalanine to tyrosine (the congenital disease phenylketonuria). Cysteine is synthesized by using sulfur from methionine, and it also may be required in the diet under certain conditions. NITROGEN BALANCE The proteins in the body undergo constant turnover; that is, they are constantly being degraded to amino acids and resynthesized. When a protein is degraded, CHAPTER 1 / METABOLIC FUELS AND DIETARY COMPONENTS 13 its amino acids are released into the pool of free amino acids in the body. Major Nitrogenous Excretion Products amino acids from dietary proteins also enter this pool. Free amino acids can have one of three fates: they are used to make proteins, they serve as precursors for synthesis of essential nitrogen-containing compounds (e. When amino acids are oxidized, their Uric acid nitrogen atoms are excreted in the urine principally in the form of urea. The urine NH 4 also contains smaller amounts of other nitrogenous excretory products (uric acid, creatinine, and NH4 ) derived from the degradation of amino acids and com- pounds synthesized from amino acids (Table 1. Some nitrogen is also lost in sweat, feces, and cells that slough off. Multiple vitamin deficiencies Nitrogen balance is the difference between the amount of nitrogen taken into accompanying malnutrition are far the body each day (mainly in the form of dietary protein) and the amount of more common in the United States nitrogen in compounds lost (Table 1. If more nitrogen is ingested than than the characteristic deficiency diseases excreted, a person is said to be in positive nitrogen balance. Positive nitrogen associated with diets lacking just one vitamin, balance occurs in growing individuals (e. Con- The characteristic deficiency diseases arising versely, if less nitrogen is ingested than excreted, a person is said to be in nega- from single vitamin deficiencies were often identified and described in humans through tive nitrogen balance. A negative nitrogen balance develops in a person who is observations of populations consuming a eating either too little protein or protein that is deficient in one or more of the restricted diet because that was all that was essential amino acids. Amino acids are continuously being mobilized from body available. If the diet is lacking an essential amino acid or if the intake of protein was discovered by a physician in Java, who is too low, new protein cannot be synthesized, and the unused amino acids will related the symptoms of beri-beri to diets be degraded, with the nitrogen appearing in the urine. If a negative nitrogen bal- composed principally of polished rice. Today, ance persists for too long, bodily function will be impaired by the net loss of crit- single vitamin deficiencies usually occur as a ical proteins. In contrast, healthy adults are in nitrogen balance (neither positive result of conditions that interfere with the nor negative), and the amount of nitrogen consumed in the diet equals its loss in uptake or utilization of a vitamin or as a result urine, sweat, feces, and other excretions. For example, peripheral neuropathy associated with vitamin E deficiency can D. Vitamins occur in children with fat malabsorption, and alcohol consumption can result in beri-beri. Vitamins are a diverse group of organic molecules required in very small quan- Vegans, individuals who consume diets lack- tities in the diet for health, growth, and survival (Latin vita, life). The absence of ing all animal products, can develop deficien- a vitamin from the diet or an inadequate intake results in characteristic defi- cies in vitamin B12. The amount of each vitamin required in the diet is small (in the micro- In the hospital, it was learned that Mr. Percy Veere had lost 32 lb in gram or milligram range), compared with essential amino acid requirements (in the 8 months since his last visit to the gram range). The vitamins are often divided into two classes, water-soluble his family physician. On admission, his vitamins and fat-soluble vitamins. This classification has little relationship to hemoglobin (the iron-containing compound their function but is related to the absorption and transport of fat-soluble vita- in the blood, which carries O from the lungs 2 mins with lipids. However, some 42 135), and other hematologic indices vitamins also act as hormones. We will consider the roles played by individual vita- were also abnormal. These values are mins as we progress through the subsequent chapters of this text.
Despite these ﬁndings generic forzest 20 mg on line erectile dysfunction treatment youtube, the authors did not rule out the possibility that those receiving LD longer had a more progressive disease order forzest 20mg erectile dysfunction treatment in bangalore. Evidence indicates that conversion of dopa to dopamine can occur at sites other than dopaminergic terminals in the striatum (43,54,58). Thus, LD continues to be effective throughout the course of disease. Markham and Diamond (81,82) demonstrated this when they studied three groups of patients; those starting LD after 1–3 years of disease, 4–6 years, and 7–9 years. In this manner they could assess whether the apparent loss of efﬁcacy could relate to the disease duration or the duration of drug therapy. After 6 years of follow-up they noted the following: 1. The disability scores were different for the three groups at initiation of LD and remained different thereafter. Disability scores were the same for the three groups when they were matched for disease duration despite varied durations of therapy. There was no signiﬁcant difference with respect to the incidence of dyskinesias. In projecting the course of disease it was found that all three groups ultimately followed the same predictable course of progression independent of the duration of LD therapy. This was conﬁrmed after 12 years of follow- up of the ﬁrst group (81,82). The authors concluded that LD works at all stages of PD, does not result in tolerance over time, but does not stop progression of disease. In other words, changes in disability of PD are related to duration of disease and not duration of therapy or tolerance to LD. Aside from progression of disease, another cause of the apparent loss of efﬁcacy relates to narrowing of the therapeutic window—increased sensitivity to adverse effects such as dyskinesias and hallucinations (45,46). The worsening of disease also comes from the onset and progression of symptoms not attributable to dopamine systems, such as postural instability, freezing, and dementia (46). MORTALITY OF PD WITH LEVODOPA Several studies performed in the 1970s demonstrated that LD therapy improves mortality in PD. These studies compared the survival of LD- treated patients to the mortality rate demonstrated in the pre-levodopa Hoehn and Yahr study (2), which demonstrated that mortality was three Copyright 2003 by Marcel Dekker, Inc. Nearly all studies indicated that LD improved survival with rates of 1. Some investigators suggested that survival approached normal, while others indicated that the effect was only seen early in therapy and then disappeared. However, many of the studies have been criticized due to methodological ﬂaws, problems with patient selection, and possible biases. One study of particular interest (83) utilized a population-based study design (retrospective) to avoid many of these ﬂaws and examine the change in survival related to LD therapy. The study included patients treated from 1964 to 1978 to include patients treated early and late as well as untreated cases. Results indicated that survival for all patients was signiﬁcantly poorer than that of the general population but was better in treated than in untreated PD. Throughout the entire 17 years of follow-up there was reduced risk of death with LD therapy. One other area of interest relates to the timing of LD therapy. Does early or later intervention affect the survival rates? They divided patients into three groups: group one, 1–3 years of PD; group two, 4–6 years of PD; group three, 7–9 years of PD. They used observed-to-expected death rate (from a group of similar make-up in the general population) ratios as measures of survival. When duration of therapy is held constant at 15 years, the ratio was higher for patients with longer duration of disease. When duration of disease was held constant at 17 years, the patients in group one had a better mortality ratio than the other two groups. Thus, early initiation of LD therapy was beneﬁcial to life expectancy. They suggested that the improved survival related to the symptomatic effect of the drug, keeping patients more active in the earlier years. Of those, 98 were treated for 2 or more years while 47 were treated for <2 years. However, there were biases that led to an underestimation of mortality in the delayed treatment group, including 47 patients who were lost to follow-up. They concluded that survival from early LD initiation is the same or better than late. IS THERE AN ASSOCIATION BETWEEN LD THERAPY AND MELANOMA? Previous reports as well as the Physician’s Desk Reference caution against the use of LD in PD patients with a history of melanoma.
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