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Biomedical subjects

S E Kahn

Publications and source records attributed to S E Kahn.

135 records · Page 8Linked to original sources
PubMed1979

Identification, characterization and localization of a (Ca2+ + Mg2+)-activated purine nucleoside triphosphate phosphohydrolase from calcifying cartilage.

A purine nucleoside triphosphate phosphohydrolase (unspecified diphosphate phosphohydrolase, EC 3.6.1.15) was chromatographically separated from the bulk of alkaline phosphatase activity by gel filtration chromatography of butanol and EDTA extracts of fracture callus and bovine epiphyseal cartilage. The callus enzyme differed from alkaline phosphatase in a variety of characteristics. The purine nucleoside triphosphate phosphatase hydrolyzed a more specific group of substrates, required Ca2+ and Mg2+ for optimal activity, remained unaffected by a potent alkaline phosphatase inhibitor, and demonstrated a narrower range of optimal pH for catalytic activity. The enzyme was localized in the microsomal pellet following subcellular fractionation of callus chondrocytes. These characteristics indicate a role for the enzyme in Ca2+ transport.

Alkaline Phosphatase↗
PubMedDate not supplied

Insulin binding to brain capillaries is reduced in genetically obese, hyperinsulinemic Zucker rats.

In order to study the role of plasma insulin in regulating the binding of insulin to the endothelium of the blood-brain barrier (BBB), insulin binding to a purified preparation of brain capillaries was measured in both genetically obese Zucker rats and lean Zucker controls. We found a reduction of 65% in brain capillary insulin binding site number in the obese compared to lean rats with no change in receptor affinity. Furthermore, specific insulin binding to brain capillaries was negatively correlated (p less than 0.05) to the plasma insulin level, suggesting a role for plasma insulin in regulating insulin binding. A similar relationship was observed between insulin receptor number in liver membranes and the plasma insulin level. We conclude that obese, hyperinsulinemic Zucker rats exhibit a reduction in the number of BBB insulin receptors, which parallels the reduction seen in other peripheral tissues. Since insulin receptors have been hypothesized to participate in the transport of insulin across the BBB, the reduction observed in the obese rats may account for the decrease in cerebrospinal fluid insulin uptake previously demonstrated in these animals.

Animals↗
PubMedDate not supplied

Case report: clinical pathological correlations in a case of primary parathyroid carcinoma.

Carcinoma of parathyroid accounts for one to two percent of patients with primary hyperparathyroidism. A patient admitted to our medical center gave us the opportunity to follow the course of the clinical laboratory findings and the effect of treatment modalities on these laboratory measurements. The clinical course included hypercalcemia, hypophosphatemia, pancreatitis, consumptive coagulopathy, pancytopenia, and sepsis. As vitamin D3 plays and important role in calcium homeostasis, 1,25-(OH)2- vitamin D3 was measured at several points during the clinical course. These finding may serve to help understand some of the underlying control mechanisms involved in the hypercalcemic state.

Adenocarcinoma↗
PubMedDate not supplied

Serum creatinine determination by high performance liquid chromatography and five automated chemistry analyzers.

A sensitive and specific procedure is described for the determination of serum creatinine by reverse phase high performance liquid chromatography. The method involves sample pretreatment with a cation exchange resin followed by the isocratic separation of creatinine and an external standard which are detected by their absorbances at 254 nm. The analytical recovery of creatinine from serum was 99.8 +/- 4.9 percent using this method. The between-day coefficients of variation for creatinine concentrations of 0.83 and 8.63 mg per dl were 3.07 percent and 3.2 percent, respectively. Results obtained with this reference method were compared to results obtained with five automated chemistry analyzers. The results showed that while the comparison methods correlated well with the reference method (r greater than 0.98 in all cases), those comparison methods based on the Jaffe reaction showed negative biases. In some cases, these biases were highly statistically significant. The difference between paired results obtained with some of the automated Jaffe-based assays exceeded 0.20 mg per dl in a substantial number of specimens with creatinine concentration in the range of 0.5 to 2.3 mg per dl. The measurement of acetoacetate concentrations of specimens submitted to our laboratory for serum creatine assays showed that interference by this substance with certain Jaffe-based assays could result in clinically significant false elevations in serum creatinine concentrations.

Acetoacetates↗
PubMedDate not supplied

An evaluation of a spectrophotometric scanning technique for measurement of plasma hemoglobin.

The measurement of plasma hemoglobin is utilized in the evaluation of various hemolytic disorders. The purpose of this report is to illustrate the advantages of a direct spectrophotometric scanning technique for determination of of plasma hemoglobin. This method does not require the use of carcinogenic reagents. The scanning method demonstrates linearity, precision, and sensitivity suitable for clinical use and is not affected by the presence of bilirubin.

Benzidines↗
PubMedDate not supplied

Effect of bromide and iodide on chloride methodologies in plasma or serum.

The effect of adding known amounts of bromide and iodide to a plasma pool an several methodologies for measuring chloride ion has been studied. Methods evaluated were coulometric, colorimetric, and ion-specific electrode. Three different types of electrodes were evaluated in order to assess any improvements which might have been made in recent years. The older electrode methodology showed an extremely large positive error in apparent chloride ion concentration in presence of very small amounts of bromide and iodide. Also, there was a delayed return to normal response by this electrode after exposure to bromide or iodide. Both of these problems have essentially been eliminated by the newer electrodes which show responses to added bromide or iodide which are similar to the coulometric and colorimetric methods.

Blood Chemical Analysis↗