Monoclonal antibody Mab D1.1 recognizes on human melanoma cells a ganglioside antigen characterized by an alkali-labile O-acetylated sialic acid residue. Immunochemical analysis showed that this molecule is an O-acetylated product of the neuroectoderm-associated disialoganglioside GD3. Controlled chemical O-acetylation of purified GD3 resulted in the generation of this same epitope. Lysates of human melanoma cells were found to contain O-acetyltransferase activity capable of generating the antigenic epitope recognized by Mab D1.1. Thus, the addition of a single O-acetyl group to a common cell surface-associated ganglioside can create a potentially tumor-specific antigen.

Acetylation↗

PubMed1984

A monoclonal antibody recognizes an O-acylated sialic acid in a human melanoma-associated ganglioside.

Monoclonal antibody D1.1 originally prepared against the B49 cell line derived from a rat brain tumor was shown to react with a ganglioside present in fetal rat brain. We have found that this antigen is also present in human malignant melanoma tumors as well as many melanoma cell lines. The ganglioside from human melanoma cell lines migrates between GM1 and GM2 on one-dimensional thin layer chromatography. Analysis by two-dimensional thin layer chromatography with intermediate ammonia treatment suggests that the ganglioside contains one or more base-labile O-acyl esters. Mild base hydrolysis under conditions known to remove O-acyl esters results in complete loss of antigenic reactivity. Thus, the alkali-labile moiety is a critical component of the epitope recognized by the antibody. Analysis of the sialic acids of total gangliosides from [6-3H]glucosamine-labeled melanoma cells showed that approximately 10% of these molecules are O-acylated. Similar analysis of the purified ganglioside showed that greater than 30% of the sialic acids comigrated with authentic 9-O-acetyl-N-acetylneuraminic acid. The antibody did not cross-react with normal human skin melanocytes nor with any of a large number of normal human adult and fetal tissues. The antibody also did not react with numerous other malignant cell lines studied. These findings suggest that the antigenic epitope defined by antibody D1.1 contains an O-acylated sialic acid and may arise from aberrant O-acetylation occurring in human malignant melanoma cells.

Animals↗

PubMed1981

Identification of a variant of mucolipidosis III (pseudo-Hurler polydystrophy): a catalytically active N-acetylglucosaminylphosphotransferase that fails to phosphorylate lysosomal enzymes.

Fibroblasts from patients with I-cell disease (mucolipidosis II) or with pseudo Hurler polydystrophy (mucolipidosis III) are markedly deficient in UDP-N-acetylglucosamine:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase. As a consequence, the common phosphomannosyl recognition marker of acid hydrolases is not regenerated, and these enzymes are not targeted to lysosomes. We have developed a sensitive assay for the transferase that uses alpha-methyl mannoside as an acceptor, and this has allowed us to distinguish between fibroblasts from these two types of patients. The enzyme activity is less in the former than in the latter (less than 0.4-2.0 pmol/mg per hr vs 2.9-39.4). This may provide an explanation for the difference in clinical severity between the two syndromes, However, in two siblings with pseudo Hurler polydystrophy (GM 3392), the enzyme activity was normal when assayed by using alpha-methyl mannoside as acceptor whereas it was low when assayed with endogenous glycoprotein acceptors or with human placental beta-hexosaminidase A. The apparent Km values of the mutant enzyme toward alpha-methyl mannoside, high-mannose oligosaccharides, and UDP-GlcNAc were not different from those of the normal enzyme. Mixing experiments demonstrated that the mutant fibroblasts contained endogenous acceptors and were free of inhibitors. We conclude that the N-acetylglucosaminylphosphotransferase in the mutant fibroblasts has normal catalytic activity but is defective in the ability to recognize lysosomal enzymes as specific substrates for phosphorylation. This variant form of pseudo Hurler polydystrophy demonstrates the biological importance of this recognition mechanism in the generation of the phosphomannosyl marker.

Glucosyltransferases↗

PubMed1979

Value of second lumbar puncture in confirming a diagnosis of aseptic meningitis. A prospective study.

In patients with viral meningitis, polymorphonuclear leukocytes sometimes predominate in the CSF on initial examination. In a prospective analysis of this phenomenon, 16 consecutive patients with viral meningitis were followed up with serial CSF studies. The percentage of polymorphonuclear leukocytes showed a significant fall between initial and second examinations (41.75 +/- 27.0 to 8.6 +/- 8.78 [mean +/- 2 SD], P less than .001), while total WBC counts and the protein and sugar content levels remained unchanged. Based mainly upon this "polymorph shift," antibiotic therapy was correctly withheld from 100% of patients reexamined. On subsequent examinations, the percentage of polymorphonuclear cells remained low. All patients recovered completely without any specific treatment. In otherwise healthy subjects with the aseptic meningitis syndrome, antibiotic therapy can be withheld even when polymorphonuclear cells predominate on initial CSF examination. If suspicion arises regarding the diagnosis, another examination will demonstrate a significant fall in polymorphonuclear cells if the initial impression was correct.

Adult↗

PubMed1979

Typhlitis in acute leukemia: successful treatment by early surgical intervention.

Inflammation of the cecum ("typhlitis") has been an unusual, but generally fatal complication of severe granulocytopenia and immunosuppression, occurring during the therapy of hematological malignancies. The diagnosis has usually been made only at autopsy, and early surgical intervention has often been withheld because of the patient's precarious hematological status. We report here a patient in whom the clinical diagnosis of typhlitis led to early operation, with intensive blood component support. The successful outcome suggests that such an approach might improve the usually grim prognosis in patients whose underlying malignancy offers a clear chance for remission.

Agranulocytosis↗

PubMed1979

Effects of cervical dislocation on colony-forming cells in murine marrow cultures.

Bone marrow obtained in a conventional manner after killing mice by cervical dislocation demonstrates increased absolute numbers of GM-CFC when compared to that from living anesthetized mice. The anesthetic agent does not account for the observed difference. Interpretation of all studies of murine marrow culture must take this observation into account, and extrapolation of the results of such studies to living human marrow should be made with care. Further studies of the mechanisms by which cervical dislocation increases the numbers of GM-CFC may help to elucidate certain mechanisms of commitment of the pluripotential hemopoietic stem cell.

Animals↗

PubMed1978

Serum myoglobin in acute myocardial infarction: a clinical study and review of the literature.

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