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Biomedical subjects

L Lang

Publications and source records attributed to L Lang.

47 records · Page 3Linked to original sources
PubMed1985

Lysosomal enzyme phosphorylation in human fibroblasts. Kinetic parameters offer a biochemical rationale for two distinct defects in the uridine diphospho-N-acetylglucosamine:lysosomal enzyme precursor N-acetylglucosamine-1-phosphotransferase.

The primary genetic defect in the lysosomal storage disease mucolipidosis III (ML III) is in the enzyme uridine diphospho-N-acetylglucosamine:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase. This enzyme has two well-defined functions: specific recognition of lysosomal enzymes (recognition function) and phosphorylation of their oligosaccharides (catalytic function). Using fibroblasts from patients with ML III as the source of enzyme, and alpha-methylmannoside and two lysosomal enzymes as the substrates, we have identified defects in both of these functions. In one group of fibroblasts, the catalytic activity of the N-acetylglucosaminylphosphotransferase is decreased while the ability to recognize lysosomal enzymes as specific substrates remains intact. In the second group of fibroblasts, the ability to recognize lysosomal enzymes is impaired while the catalytic activity of the enzyme is normal. These data provide a biochemical rationale for the previously described genetic heterogeneity among patients with ML III (Honey, N. K., O. T. Mueller, L. E. Little, A. L. Miller, and T. B. Shows, 1982, Proc. Natl. Acad. Sci. USA., 79:7420-7424).

Acid Phosphatase↗
PubMed1984

Lysosomal enzyme phosphorylation. Recognition of a protein-dependent determinant allows specific phosphorylation of oligosaccharides present on lysosomal enzymes.

We have investigated the basis for the specific recognition of lysosomal enzymes by UDP-GlcNAc:lysosomal enzyme N-acetylglucosaminylphosphotransferase. This enzyme is responsible for the selective phosphorylation of mannose residues on lysosomal enzymes. Two mammalian lysosomal enzymes, cathepsin D and uteroferrin, and two nonlysosomal glycoproteins were treated with endo-beta-N-acetylglucosaminidase H to remove those high mannose oligosaccharide units which are accessible on the native protein. These proteins were then tested as inhibitors of three different glycosyltransferases. The endo H-treated lysosomal enzymes were shown to be specific inhibitors of the phosphorylation of intact lysosomal enzymes. Proteolytic fragments of cathepsin D, including the entire light chain and heavy chain, did not retain the ability to be recognized by the N-acetylglucosaminylphosphotransferase. These findings indicate that the intact protein portion of lysosomal enzymes contains a specific recognition determinant which leads to high-affinity binding to the N-acetylglucosaminylphosphotransferase. The expression of this determinant appears to be dependent on the conformation of the protein.

Acetylglucosaminidase↗
PubMed1976

A new, more sensitive tube test for pregnancy evaluated with a selected hospital population.

A new tube test for pregnancy, having a sensitivity of 0.5 I.U. of human chorionic gonadotropin per milliliter, was evaluated, along with two other commercially available kits, in a hospital patient population. Of 586 patients in the study, 302 were in nonobstetric services and many were acutely ill. Approximately one fourth of the women were age 40 or older. The medical records of 66% of the patients were retrieved to obtain information on the drugs administered prior to pregnancy testing. A small number of problems did occur in the pregnancy test procedures. Inconclusive results were recorded for both pregnant and nonpregnant patients and could not be correlated with disease states and/or medications. The importance of a reagent control for tube test procedures is discussed.

Chorionic Gonadotropin↗
PubMed1975

Conductance recording of ionic outflow from frog skin glands during nerve stimulation.

A method for continuous recording of the ionic efflux from frog skin glands has been developed which under given experimental conditions provides a convenient index on glandular secretion. A nerve skin preparation from the calf is mounted so that the outside of the skin forms the bottom of a small test compartment with distilled water while the corium side is bathing in Ringer's solution. After determination of the adequate nerve stimulus parameters for discernible gland secretion to occur, the skin nerve was stimulated at 10 Hz during varying periods and chemical control analyses performed of the changes in ionic content of the test compartment solution. The main ionic outflow consisted of Na+ and Cl- in equal amounts, the outflow of other ions during stimulation being negligible. The concomitant conductance changes were measured as variations of absorption in a high-frequency field applied to a conductance probe placed in the test chamber. Determinations of the NaCl outflow based on the conductance changes were in good agreement with the values obtained by chemical analysis. The continuous conductance recordings proved to give approximative information of the quantities and time relations of the glandular secretion, allowing a direct comparison with, e.g., skin potential changes.

Animals↗
PubMed1975

Quantification of mouse macrophage chemotaxis in vitro: role of C5 for the production of chemotactic activity.

Delineation of the mechanisms of macrophage accumulation at local tissue sites will further our understanding of immunologically mediated host resistance to infectious and neoplastic diseases. Since mice are frequently used for the study of immune function, we developed a method for the quantification of mouse macrophage chemotaxis in vitro. By this method it was found that the fifth component of complement is necessary for the production of chemotactic activity in mouse serum by inflammatory agents such as endotoxin or aggregated gamma globulin. The majority of macrophage chemotactic activity produced by these agents in mouse serum can be attributed to a low-molecular-weight (ca. 15,000) chemotactic factor. The data suggest that this factor is the biologically active cleavage product of the fifth component of complement, C5a.

Animals↗