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Biomedical subjects

R Geiger

Publications and source records attributed to R Geiger.

At least 55 records · Page 3Linked to original sources
PubMed1989

The application of a photon-counting camera in sensitive, bioluminescence-enhanced detection systems for nucleic acid hybridization. Ultrasensitive detection systems for protein blotting and DNA hybridization, III.

A relatively simple, bioluminescence-enhanced detection system for nucleic acid hybridization, using alkaline phosphatase as a label, was described recently (Hauber, R. & Geiger, R. (1988) Nucl. Acid Res. 16, 1213). The principle of detection is as follows: Alkaline phosphatase releases D-luciferin (Photinus pyralis) from D-luciferin-O-phosphate. Liberated D-luciferin reacts with luciferase, ATP and oxygen with light emission. Light produced is measured with a very sensitive photon counting camera system (Argus-100), allowing the visualization and localization of the specifically bound alkaline phosphatase on nitrocellulose sheets. Under non-optimized conditions the limit of detection is at present about 30 pg of pBR322. A sulphonylated nucleotide probe was used for hybridization.

Alkaline Phosphatase↗
PubMed1988

Syncatalytic inactivation of prolyl 4-hydroxylase by synthetic peptides containing the unphysiologic amino acid 5-oxaproline.

Peptides containing the unphysiological amino acid 5-oxaproline (Opr) in the sequence R1-Xaa-Opr-Gly-OR2 were found to inactivate prolyl 4-hydroxylase from chick and human origins. Of the substances investigated, compounds with aromatic substituents R1 and R2 were particularly effective when compared with those with an aliphatic group or without a C-terminal blocking group. Both affinity of the individual peptides for the enzyme and partition ratio contributed to the differences in efficiency. Benzylcarbonyl-Phe-Opr-Gly-benzyl ester was the most effective substance tested, its concentration giving 50% inactivation in 1 h being 0.8 microM. Inactivation was only observed in the presence of 2-oxoglutarate and Fe2+. The Opr peptides enhanced the decarboxylation of 2-oxoglutarate by prolyl 4-hydroxylase, the Vmax values obtained with the individual peptides being positively correlated with their inactivating efficiency. Inactivation was prevented by high concentrations of peptide substrate and ascorbate. Lineweaver-Burk kinetics experiments suggested noncompetitive inhibition with respect to peptide substrate and ascorbate. Lysyl hydroxylase was not affected by Opr peptides in concentrations of up to 1.5 mM in either the presence or absence of prolyl 4-hydroxylase. The results suggest that the oxaproline compounds are specific syncatalytic inactivators of prolyl 4-hydroxylase.

Animals↗
PubMed1988

Secreted placental alkaline phosphatase: a powerful new quantitative indicator of gene expression in eukaryotic cells.

This paper describes a novel eukaryotic reporter gene, secreted alkaline phosphatase (SEAP). In transient expression experiments using transfected mammalian cells, we demonstrate that SEAP yields results that are qualitatively and quantitatively similar, at both the mRNA and protein levels, to parallel results obtained using established reporter genes. However, SEAP offers significant advantages in terms of ease of assay and assay expense, and also has the potential for quantitative assay at levels as low as 0.2 pg/ml of culture medium. These attributes suggest that SEAP may have general utility in experiments which rely on the accurate measurement of reporter gene expression levels.

Alkaline Phosphatase↗
PubMed1988

Schilder disease (1912): report of a case.

We describe a case of Schilder disease in a young woman pointing out the most reliable diagnostic criteria for differentiating the disease from adrenoleukodystrophy. We stress the diagnostic usefulness of ultrastructural analysis, even of poorly preserved specimens.

Adrenoleukodystrophy↗
PubMed1988

Comparison of reaction rates in trypsin-catalysed transamidation of porcine insulin and its B29-arginine analogue.

[B29-Arginine]porcine insulin was prepared from des-(B23-30)-insulin and synthetic octapeptide with the aid of trypsin. Comparison of reaction rates in trypsin-catalysed transamidation of this compound and porcine insulin with threonine ether ester showed that this reaction is determined only by conformational effects and structural features of amino acids leaving from and entering into B30, not by the structure and the pKa value of the basic amino acid in B29.

Amides↗
PubMed1988

A new type of ultrasensitive bioluminogenic enzyme substrates. I. Enzyme substrates with D-luciferin as leaving group.

Derivatives of D-luciferin, D-luciferin methyl ester, D-luciferin O-sulfate, D-luciferin O-phosphate, D-luciferyl-L-N alpha-arginine and D-luciferyl-L-phenylalanine were used as highly sensitive substrates for carboxylic esterase, arylsulfatase, alkaline phosphatase and carboxypeptidases A, B and N. Enzymatic cleavage of the compounds by enzymes leading to the release of D-luciferin was demonstrated. Kinetic constants have been determined for D-luciferin methyl ester and carboxylic esterase, for D-luciferin O-sulfate and arylsulfatase, for D-luciferin O-phosphate and alkaline phosphatase, for D-luciferyl-L-phenylalanine and carboxypeptidase A, and for carboxypeptidases B and N and D-luciferyl-L-N alpha-arginine. All compounds proved to be highly sensitive substrates for the respective enzymes, permitting a limit of detection for enzymes between 10 and 500 fg per assay.

Alkaline Phosphatase↗
PubMed1988

Determination of leukocyte elastase-inhibitor complexes and leukocyte neutral proteinase inhibitor by enzyme immunoassays. Leukocyte elastase-inhibitor complexes in porcine blood, III.

Sensitive enzyme immunoassays for the determination of total leukocyte neutral proteinase inhibitor and polymorphonuclear elastase-leukocyte neutral proteinase inhibitor complexes are described. The usable ranges of the standard curves were from 80 ng/l to 10 micrograms/l. The relative intra-assay coefficients of variation of the tests were between 2 and 4%, and the inter-assay coefficients of variation between 4 and 10%. In vitro and in vivo studies were performed with septic pigs and isolated leukocytes. The results show that leukocyte neutral proteinase inhibitor can be used in pigs as a parameter for the development of a septicaemia.

Animals↗