Biomedical subjects

L E Seargeant

Publications and source records attributed to L E Seargeant.

27 records · Page 2Linked to original sources

PubMed1987

In vitro stability and compatibility of daunorubicin, cytarabine, and etoposide.

The continuous infusion of cytarabine, daunorubicin, and etoposide offers several theoretical advantages over bolus infusion in the treatment of acute nonlymphocytic leukemia. To date, this approach has been limited by the need for three separate iv lines. The in vitro stability and compatibility of these three agents were therefore evaluated. Solutions of 200 mg of cytarabine, 25 mg of daunorubicin, and 300 mg of etoposide per 750 ml of 5% dextrose and 0.45% saline were prepared alone and in combination. The solutions were evaluated visually, spectrophotometrically, and by high-pressure liquid chromatography (HPLC) twice daily for 72 hours. Precipitates or color changes were not noted. Changes in the patterns of the spectral scans and chromatographs were not observed. Concentrations of the drugs as assessed by HPLC were stable over the 72-hour period of observation for both individual and combined drug preparations. In conclusion, cytarabine, daunorubicin, and etoposide are stable and compatible in vitro for at least 72 hours. These drugs can therefore be administered together by continuous infusion using a single iv line.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1984

Homocystinuria and megaloblastic anemia responsive to vitamin B12 therapy. An inborn error of metabolism due to a defect in cobalamin metabolism.

We describe an inborn error of vitamin B12 metabolism in an infant who had severe developmental delay, megaloblastic anemia, and homocystinuria. There was no evidence of methylmalonic aciduria or deficiency of folate or vitamin B12. Treatment with hydroxocobalamin, but not with cyanocobalamin and folic acid, resulted in rapid clinical and biochemical improvement. Cultured fibroblasts showed an absolute growth requirement for methionine, defective incorporation of radioactivity from [14C]5-methyltetrahydrofolate into protein, and normal incorporation of radioactivity from [14C]propionate, thus assigning the intracellular defect to methionine synthesis. The proportion of intracellular methylcobalamin in the fibroblasts was decreased, but that of 5'-deoxyadenosylcobalamin was normal. Methionine synthetase activity in cell extracts was normal, as was cobalamin incorporation into cultured cells. This defect differs from those described previously in being limited to methylcobalamin accumulation and defective use of 5-methyltetrahydrofolate by intact cells with normal activity of methylmalonyl CoA mutase.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗

PubMed1981

Comparative studies of pure alkaline phosphatases from five human tissues.

The alkaline phosphatases present in the human tissues liver, kidney, intestine, placenta and a serum from a patient with Paget's disease of bone have been purified to apparent homogeneity by affinity elution from a phosphonic acid-Sepharose derivative. Polyacrylamide gel electrophoresis in SDS gave subunit molecular weights ranging from 74 000 for the enzyme form placenta to 95 800 for the enzyme from kidney. The purified native and desialylated enzymes have been characterized by agar electrophoresis and isoelectric focusing. All five of the native enzymes behaved differently but the desialylated forms from liver, Paget's serum and kidney were indistinguishable in both systems. The desialylated enzyme from placenta and the enzyme from intestine behaved differently from each other and from the above mentioned group. The isoelectric points ranged from less than 4 for the native enzyme from liver to 7.01 for the desialylated forms of the enzymes from liver, kidney and Paget's serum. The effects of a number of factors on the thermostability of the purified enzymes were studied. Phosphate decreased the stability and human serum albumin increased the stability of most molecular forms. Desialylation had no effect on thermostability. These results and those from inhibition studies with L-phenylalanine, L-homoarginine, phosphate and vanadate support the 3-gene hypothesis advanced from structural studies.

Alkaline Phosphatase↗

PubMed1979

Evidence that three structural genes code for human alkaline phosphatases.

The number of structural gene loci that code for the different molecular forms of human alkaline phosphatase is unknown. Physical properties of the enzymes, immunological data, chemical inhibition and genetic studies suggest that at least three structural genes are involved: one coding for alkaline phosphatase from placenta, another for the enzyme from intestine, and one or more for the enzymes from liver, kidney and bone. Badger and Sussman have shown that alkaline phosphatases from human liver and placenta are products of different structural genes, and Greene and Sussman have shown that alkaline phosphatase from a metastasised bronchogenic carcinoma was nearly identical to the enzyme from placenta. However, other tumour-associated alkaline phosphatases and the enzymes from normal tissue other than placenta and liver have not been identified by conclusive structural criteria, and thus it is not known whether these onco-alkaline phosphatases represent ectopic production or unusual post-translational modification of the enzymes found in normal tissues. We present here, using a sensitive peptide-mapping technique, structural evidence that the enzyme forms from liver, kidney and serum from a patient with Paget's disease of bone (osteitis deformans) are products of the same structural gene and can be easily distinguished from either the intestinal or placental isoenzymes. The technqiue seems to be useful for the classification of tumour-associated alkaline phosphatases on a structural basis.

Alkaline Phosphatase↗

PubMed1979

Inhibition of human alkaline phosphatases by vanadate.

Orthovanadate was shown to be a potent competitive inhibitor (Ki less than 1 microM) of purified alkaline phosphatase from human liver, intestine of kidney. Inhibition was reversed and full enzymic activity restored in the presence of 1mM-adrenaline. Phosphate and vanadate competed for the same binding site on the enzyme.

Alkaline Phosphatase↗

PubMed1979

Affinity elution from a phosphonic acid-Sepharose derivative in the purification of human liver alkaline phosphatase.

The compound p-aminobenzylphosphonic acid has been coupled via an azo linkage to tyraminyl-Sepharose 4B. This derivative at pH 6.0 bound most of the protein and all of the alkaline phosphatase in a crude preparation from human liver. The phosphatase was selectively eluted with the substrate 2-naphthylphosphate and a purification of 400-fold obtained. This step, when incorporated into a procedure for the purification of human liver alkaline phosphatase, yielded essentially pure enzyme.

Alkaline Phosphatase↗

PubMed1979

Phosphoester specificity of purified human liver alkaline phosphatase.

Kinetic parameters for the hydrolysis of a number of physiologically important phosphoesters by purified human liver alkaline phosphatase have been determined. The enzyme was studied at pH values of 7.0 to 10.0. The affinity of the enzyme for the compounds was determined by competition experiments and by their direct employment as substrates. Phosphodiesters and phosphonates were not hydrolysed but the latter were inhibitors. Calcium and magnesium ions inhibited the hydrolysis of ATP and PP1 and evidence is presented to show that the metal complexes of these substrates are not hydrolysed by alkaline phosphatase. A calcium-stimulated ATPase activity could not be demonstrated for the purified enzyme or the enzyme in the presence of a calcium-dependent regulator protein. Nevertheless, the influence of magnesium and calcium ions on the ATPase activity of alkaline phosphatase means that precautions must be taken when assaying for Ca2+-ATPase in the presence of alkaline phosphatase. The low substrate Km values and the hydrolysis which occurs at pH 7.4 mean that the enzyme could have a significant phosphohydrolytic role. However, liver cell phosphate concentrations, if accessible to the enzyme, are sufficient to strongly inhibit this activity.

Adenosine Triphosphate↗

PubMed1976

Affinity purification and some molecular properties of human liver alkaline phosphatase.

Alkaline phosphatase from human liver was purified to homogeneity. The purification procedure included solubilization with butanol, fractionation with acetone, and chromatography on concanavalin A-Sepharose, DEAE-cellulose, Sephadex G-200 and DEAE-Sephadex. Purity was established by standard and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The isoelectric point of the protein was determined to be 4.0. Sephadex-gel filtration gave a mol.wt. of 146000, although a higher value was obtained in the presence of 100mM-NaC1. The subunit mol.wt. 76700, was determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Neuraminidase treatment resulted in two enzyme-activity bands on isoelectric-focused gels with isoelectric points of 6.6 and 6.8. The desialylated enzyme gave only one protein band on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis with a subunit molecular weight indistinguishable from that of the non-neuraminidase-treated protein. The desialylated enzyme was more readily denatured by sodium dodecyl sulphate in the presence of mercaptoethanol than was the native enzyme.

Alkaline Phosphatase↗

PubMedDate not supplied

Familial neuroblastoma: report of a kindred with later age at diagnosis.

PURPOSE: To describe the clinical and biologic features of neuroblastoma (NB) in two siblings and their maternal second cousin. PATIENTS AND METHODS: NB was diagnosed in the siblings at 2 1/2 (patient 2) and 5 (patient 3) years of age. NB was diagnosed in their maternal second cousin (patient 1) when she was 7 years old. Standard clinical and biological data, tumor karyotype, and tumor allelotype at select loci were obtained. RESULTS: Patient 1 had International Neuroblastoma Staging System (INSS) stage 4 NB and unfavorable histology but no evidence of MYCN amplification; she died from complications of autologous bone marrow transplantation in second remission. Patient 2 had INSS stage 4 NB with unfavorable histology but no MYCN amplification; her disease recurred 39 months after completing therapy. Patient 3 had INSS stage 1 NB with favorable biologic features; he was treated with surgical excision and remains free of disease. CONCLUSIONS: Familial NB may occur at a later age than predicted by the tumor suppressor gene model of inherited cancer. This report further emphasizes the clinical and biological heterogeneity of familial NB.

Age of Onset↗