Showing papers in "Advances in Clinical Chemistry in 1971"

Biochemical Aspects of Muscle Disease

Abstract: Publisher Summary Voluntary muscle disease can result from a variety of causes. Muscle diseases can be divided and subdivided according to their etiology. Many are very rare and have not yet been the subject of biochemical investigations. The major biochemical efforts have been directed toward the genetically determined myopathies, especially the muscular dystrophies and, to a lesser degree, the myotonic disorders and some of the more common muscle disorders of established neurogenic origin. Although numerous changes in the chemical constituents of blood and urine have been observed in patients with muscle diseases, the biochemical abnormalities can be adequately studied only by a direct investigation of the diseased muscle. It is difficult to procure a sufficient number of samples of biopsied muscle from patients. The tissue donated is often from relatively advanced cases, where the degree of muscular degeneration is so extreme as to mask the earlier and more meaningful changes. The recognition of Duchenne type muscular dystrophy in the very early stages by serum enzyme changes is of some help in this respect, but the provision of adequate quantities of suitable muscle is still a difficulty.

Immunoglobulins in clinical chemistry.

Abstract: Publisher Summary This chapter discusses the clinical applications of immunoglobulins, the deficiencies, the increases, and the neoplasias. The word immunoglobulin refers to “that kind of protein in which specific antibody activity can be found.” The term is now preferred to γ-globulin because this can be confused with the commonest immunoglobulin class, γ G-globulin and also because immunoglobulins can be found with electrophoretic mobilities anywhere between the α 1 and the post-γ positions. The chapter describes the structure and identification of immunoglobulins. With standardized reactions between a class-specific antiserum and its immunoglobulin, it is possible to measure the level of that immunoglobulin in serum. The most economical assay at present utilizes radial immunodiffusion, wherein wells are made in antiserum containing agar and filled with antigen so that precipitin rings form. The crude but simple overall measurement of immunoglobulins can be useful in various areas—immune deficiency, recurrent respiratory infections, Crohn's and celiac diseases, and endocarditis.

Hereditary Metabolic Disorders of the Urea Cycle

Abstract: Publisher Summary Urea is the main end product of nitrogen metabolism. It is formed from the ammonia arising from the metabolism of the amino acids of protein by a sequence of five reactions, four of which comprise the urea cycle proper. The end result is the conversion of ammonia into urea, with the reformation of the individual reactants of the cycle. Compared with other metabolic pathways, the urea cycle is short, possibly the shortest of all. Defects of the enzymes mediating all four reactions of the urea cycle proper have now been established, and there is some evidence of the existence of a fifth enzyme defect, involving carbamyl phosphate synthetase, mediating the initial reaction of the pathway. One of the most important results of a defect of the biosynthesis of urea is an increased level of blood ammonia. Therefore, it is essential to consider other conditions that might affect indirectly the urea cycle or in some other way raise the blood ammonia. Because lysine can act as a competitive inhibitor of the conversion of arginine to ornithine and urea, an increased level of plasma lysine may therefore inhibit the urea cycle.

Rapid screening methods for the detection of inherited and acquired aminoacidopathies.

Abstract: Publisher Summary Two new developments in clinical medicine have made the early recognition of inborn metabolic errors in the clinical chemistry laboratory of increased importance Utilization of dietary regimens deficient in the metabolites normally acted upon by the missing enzyme serves to ameliorate the more serious consequences of the disease, for example, low-phenylalanine diets in cases of phenylketonuria The availability of amniotic fluid early in pregnancy by amniocentesis has made possible the prenatal diagnosis of genetic disease in those conditions in which the accumulated substance or missing enzyme is known This approach is discussed in this chapter that helps to determine whether pregnant women, who have previously given birth to children with Tay–Sachs disease, are carrying an abnormal fetus by analyzing the amniotic fluid for the missing enzyme—that is, β-D-N-acetylhexosaminidase A An early diagnosis in this situation is essential if the mother is to have a choice of ending the pregnancy or carrying the fetus to term

Multiple analyses and their use in the investigation of patients.

Abstract: Publisher Summary Grouping of tests has become an important part of laboratory investigation. In addition, screening tests and preliminary discretionary tests have also become a convenient and integral part of patient investigation. The introduction of automatic methods of analysis in clinical laboratories has led to increased possibilities in all the aspects of laboratory investigation. The combination of test groups, screening tests, and preliminary discretionary tests received further stimulus with the introduction of the simultaneous multichannel (SMA) machine. The introduction of the SMA was heralded by the company with three reasons as to why it should be used. First, analytical convenience; second, the unsolicited information produced by the equipment led to new or additional diagnoses unsuspected by the clinician; and third, preliminary discretionary tests consumes less time than the days required by the usual process of discretionary analysis. Profile analysis is now an accepted part of clinical chemical investigation. Such investigations lead to a number of patients having new or additional diagnoses, many of which lead to an alteration of treatment.

The biochemistry of skin disease: psoriasis.

Abstract: Publisher Summary This chapter reviews the biochemistry of skin disease, which is of interest to a clinical chemist. Psoriasis is the only skin disease, which has been extensively studied and whose clinical, biochemical, and physiological aspects are unfamiliar to most scientists outside dermatology. Although there are no biochemical tests, which can yet be performed in the laboratory to help confirm the diagnosis or to aid in the prognosis or choice of therapy, the biochemical enigmas encountered in the study of this disease are of interest to all biologists. Psoriasis is common, it has a definite genetic background, has uncontrolled yet not malignant growth as its outstanding feature, has disordered maturation and differentiation, has an experimental model in the Koebner reaction, and it has intense metabolic and mitotic activity. It also has material readily available for study and it offers the possibility of helping millions of people who suffer but usually do not die.

Pituitary gonadotropins--chemistry, extraction, and immunoassay.

Abstract: Publisher Summary This chapter examines the current status of immunological assays used to measure the pituitary gonadotropic hormones. All immunoassays basically depend on the interaction of an antigen of unique identity and its specific antibody. It is also necessary to discuss the chemical nature of the various preparations of Follicle stimulating hormone (FSH) and Luteinizing hormone (LH), which are currently available and to consider the concept of antibody specificity as it applies in this field. Both FSH and LH contain carbohydrate, which is easily removed by mild hydrolysis. Sialic acid is necessary for the biological, but not for the immunological, activity of FSH. Consideration is given to the importance of carbohydrate moieties in the assay of both gonadotropic hormones. FSH and LH can be extracted from pituitary tissue and from urine by a variety of methods; techniques for the purification of such extracts are also numerous.