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Biomedical subjects

E Epstein

Publications and source records attributed to E Epstein.

288 records · Page 16Linked to original sources
PubMedDate not supplied

Review of phosphate methodologies.

A description of the extensive literature on the methodologies for the determination of serum phosphate has been reviewed. The evolution of the various phases of the analytical techniques developed in the last century leading to the simplified, sensitive and accurate procedures of the present have been presented in some detail. A procedure involving a simple direct reaction for the determination of inorganic phosphate in serum using ascorbic acid as a reducing agent and a citrate-arsenite mixture as a stabilizing-sensitizing reagent, all in a semi-aqueous medium containing dimethysulfoxide and the detergent Teepol 610 is recommended. Jaundice and mild hemolysis are noninterferencts and turbidity from severe lipemia is easily overcome by reversing the sequence in which reagents are added because citrate binds molybdate in preference to phosphate. Thus, the serum blank and the reacted serum are identical in makeup thereby yielding an idealized correction for irrelevant absorption. Reaction characteristics and potential errors are included in the discussion of the procedure.

Chemical Phenomena↗
PubMedDate not supplied

Interpretation of cerebrospinal fluid proteins by gel electrophoresis.

The use of polyacrylamide gel electrophoresis (PAGE) for the separation of proteins in cerebrospinal fluid (CSF) results in greater definition than does a "routine" method such as cellulose acetate electrophoresis. Unconcentrated CSF is easily separated into as many as 18 bands by the use of PAGE. By means of a modified PAGE method described in this paper, unconcentrated and untreated CSF is quickly and conveniently analyzed for protein constituents. This modification involves a continuous buffer environment, a pore-size concentration gradient and CSF in amounts of 0.1 to 0.4 ml. Sucrose addition is not necessary in this procedure. Whereas most central nervous system (CNS) disease states do not yield consistently distinctive protein patterns, some diseases, such as vascular disease, infectious meningitis and some metastatic tumors, yield significantly altered patterns. It is suggested that the chief value of CSF protein electrophoresis at the present time is to follow the course of a CNS disease.

Buffers↗
PubMedDate not supplied

Determination of liver microsomal glucose-6-phosphatase.

A procedure for the determination of liver microsomal glucose-6-phosphatase is described. Homogenization and ultracentrifrigation were used to prepare a precipitate whose character was defined by monitoring the desire enzyme activity which serves as a marker. Activity of the enzyme was determined by means of a sensitive colorimetric reaction for the product, inorganic phosphate. Non-enzymatic hydrolysis problems with the substrate are minimized in this procedure by the masking action of citrate. The final heteropoly blue color appears to be considerably sensitized by interaction of phosphomolybdous ion with arsenite. The stability of the relatively labile enzyme was ensured by chelating any metals present with ethylene diamine tetraacetic acid. The overall results obtained by the procedure appear to be useful as an aid in the diagnosis of Type I glycogenosis, a glycogen storage disease called Von Gierke's disease.

Colorimetry↗
PubMedDate not supplied

Enzyme reagents for measurement of phospholipids of amniotic fluid.

Enzymic procedures have been developed for the specific determination of three phospholipids in an effort to make the estimation of the phospholipids of amniotic fluid more sound analytically. Apart from the actual determination of these analytes (lecithin, sphingomyelin, and phosphatidylglycerol), these enzymic procedures facilitate the evaluation of a number of the basic premises and procedural steps involved with the traditional procedures for the evaluation of fetal lung maturity. To this end, the changes are reported in sphingomyelin concentrations with gestational age. Although lacking in sufficient clinical data to assign "cut-off" values as yet, the enzymic procedures seem to correlate well with the existing procedures and are analytically accurate and precise.

Amniotic Fluid↗
PubMedDate not supplied

Detergent altered alkaline phosphatase patterns of liver disease.

A procedure has been described whereby the high molecular weight alkaline phosphatase (slow-moving) isoenzyme may be studied by means of polyacrylamide gel electrophoresis. By treatment of sera containing this isoenzyme with some detergents of the nonionic Triton octylphenoxyethanol series, the high molecular weight alkaline phosphatase isoenzyme is altered so that its electrophoretic mobility more closely resembles that of the usual alklaine phosphatase isoenzymes. The high molecular weight isoenzyme is thought to be associated with phosphatidyl choline and/or liproproteins. The detergent action is to dissociated the alkaline phosphatase from its lipid carrier. It is thought that these lipid-alkaline phosphatase complexes are associated with liver cell fragments. The detergent altered slow-moving alkaline phosphatase may migrate as a single band, from two to four new bands, or as several new bands. Liver, bone and intestinal alkaline phosphatase isoenzymes are unaffected by detergent action.

Alkaline Phosphatase↗
PubMedDate not supplied

Use of alkaline phosphatase isoenzyme analysis in the evaluation of cholestatic liver disease.

A useful laboratory test for the differentiation of liver, bone, and intestinal alkaline phosphatase (ALP) isoenzymes in serum is presented. Electrophoresis in polyacrylamide gel is performed with untreated serum as well as with serum incubated at 56 degrees C for 10 min. The heating step denatures bone isoenzyme which may obscure the liver ALP band when present in large amounts. Visualization of ALP activity is accomplished by the use of buffered p-toluidinium 5-bromo-4-chloro-indolyl phosphate and magnesium ions. In serum of patients with cholestatic liver disease, the occurrence of large molecular weight liver cell membrane fragments which contain ALP activity is postulated. These ALP-containing fragments occur at the origin of the electrophoretogram, unable to penetrate the small pore separation gel. Abnormalities involving ALP isoenzymes, such as bone isoenzyme arising from increased osteoblastic activity, may be detected. Intestinal isoenzyme, normally present in small amounts in some subjects of blood groups B or O, may be elevated in certain liver diseases, such as cirrhosis. By the use of this method the routine question of whether an ALP found to be increased in a screening procedure is due to liver or bone abnormality may be answered. In addition, the occurrence of abnormal ALP bands arising from cholestatic conditions and the occurrence of abnormal amounts of intestinal isoenzyme may also be detected.

Alkaline Phosphatase↗
PubMedDate not supplied

Enzyme defects in hereditary porphyria.

Heme is an important prosthetic group for proteins concerned with energy metabolism. All cells in the body probably make heme, but nucleated erythroid and hepatic cells have been studied the most. Feedback control of heme formation differs in the red cells and in the liver. About eight enzymes have a place in the formation of heme. Defects in the enzyme pathways may be the result of genetic abnormalities and phenotypically occur as hereditary porphyrias. If the major defect occurs in the red cell line, erythropoietic porphyrias occur; if the liver has the major defect, than hepatic porphyrias are present. There are probably three erythropoietic porphyrias and four hepatic porphyrias which are genetically determined. However, some are not clearly classified,--with erythropoietic protoporphyria involving hepatic and erythroid cells and porphyria cutanea tarda not being a clear cut genetic abnormality, at least some of the time. Elucidation of the genetic enzymatic defects introduces new diagnostic tools and also has led to at least one revolutionary new treatment for some hepatic porphyrias.

5-Aminolevulinate Synthetase↗
PubMedDate not supplied

Some aspects of bilirubin determination in the newborn using dimethyl sulfoxide.

Although serum bilirubin determination is a common procedure in most clinical laboratories, the test seems to be of particular importance in the screening of neonates, especially the premature or the erythroblastotic infant. However, bilirubin determination is subject to interferences, particularly in the presence of hemolysis and lipemia, which may seriously affect the results. It is, therefore, of paramount importance to the pediatrician to be aware of these potential shortcomings of the test. To improve the reliability of bilirubin determination, a method using dimethyl sulfoxide is proposed which is simple, rapid, and ideally-suited for small amounts of blood such as are commonly encountered in pediatrics. The effect of hymolysis and moderate lipemia are minimal, and the use of a sample blank can usually be eliminated in most circumstances.

Bilirubin↗
PubMedDate not supplied

Associated problems of protein electrophoresis, staining and densitometry.

The process of electrophoresis, a separation phenomenon, is mistakenly understood to include the sequential processes ancillary to analyte resolution, that is, staining and quantification, where the latter could be elution followed by photometry or integrating-calculating-densitometry. The theories involved in electrophoresis itself are well worked out and equally well understood but the problems which are associated with separation, chemical reaction to generate a chromogen and quantification, perhaps partly forgotten and perhaps partly ignored, are taken up and described here. They include albumin trail, resolution, unequivalent staining, prestaining and the densitometry problems associated with band widths, opacity effects and polychromaticities.

Blood Proteins↗
PubMedDate not supplied

Monitoring the administration of methotrexate in antimetabolite therapy.

An enzymatic method for the measurement of methotrexate (MTX) in serum is presented in which the inhibition of the enzyme dihydrofolate reductase by MTX is measured. Reduction of the substrate dihydrofolate by the enzyme and cofactor NADPH is lessened in direct proportion to the amount of MTX present. Measurements can be made in the "therapeutic range" of MTX which corresponds to the 10(-7) to 10(-8) M concentration of MTX in serum.

Folic Acid↗
PubMedDate not supplied

Simple, direct determination of serum 5'-nucleotidase.

A simple determination of 5'-Nucleotidase in blood serum without deproteinization is described. The enzyme activity is distinguished from that of a nonspecific alkaline phosphatase by nickel inhibition and the inorganic phosphate released from adenosine monophosphate used as substrate is determined by a method previously described. Additional studies include the determination of optimal conditions for the reaction and nickel inhibition.

Alkaline Phosphatase↗
PubMedDate not supplied

Comparative sensitivities of flame atomic absorption spectrophotometry (AAS) and molecular absorption spectrophotometry (MAS).

A sensitivity comparison was made between conventional atomic absorption spectrophotometry (AAS) and conventional molecular absorption spectrophotometry (MAS) for the serum trace metals, copper, iron, and zinc. The sensitivity aspect considered was absorbances was obtained for concentrations in the solutions analyzed using unit lightpaths of 1 cm and 10 cm for MAS and AAS, respectively. A distinction was made between procedural sensitivity and measurement sensitivity where the latter represents molar absorptivity. Some was given to the concepts of procedural sensitization by concentration of the analyte through the use of lyophilization, extraction or ashing. The misuse of data obtained with scale expanders is described as a commonly occurring phenomenon of both AAS and MAS and a source of confusion in the understanding of measurement sensitivity.

Copper↗