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Biomedical subjects

N W Barton

Publications and source records attributed to N W Barton.

64 records · Page 4Linked to original sources
PubMed1983

Neurological complications of Kaposi's sarcomat. An analysis of 5 cases and a review of the literature.

We analyzed the neurological complications in 25 patients with Kaposi's sarcoma, 5 encountered at Memorial Sloan-Kettering Cancer Center and 20 culled from the literature. Patients with all clinical forms of Kaposi's sarcoma [14 classical cases, 2 African cases, 5 cases associated with immunosuppressive therapy and 4 cases associated with acquired immunodeficiency syndrome (AIDS)] suffered neurological dysfunction which included neoplastic involvement of the nervous system (Kaposi's sarcoma or another primary), autoimmune disorders and opportunistic infections. Neoplastic involvement was recorded most frequently in patients with classical and African Kaposi's sarcoma and was favored in a setting of extensive tumor dissemination. Opportunistic infections (cryptococcal meningitis and cerebral toxoplasmosis) were observed in all forms of Kaposi's sarcoma but were most frequent in AIDS cases and correlated with the degree of immune dysfunction. Our data suggest that more diverse opportunistic central nervous system infections, neurological disorders of an autoimmune nature, and neoplastic involvement of the nervous system are to be anticipated in AIDS.

Adult↗
PubMed1979

Accessibility of sialo components in a murine tumor cell to extracellular N-acetylneuraminate glycohydrolase (sialidase).

Lipid-bound sialic acid in the murine melanoma cell is not totally inaccessible to an exogenous macromolecular probe, as formerly believed. Roughly 30% of the dialic acid bound to lipid, and an equal proportion of the sialic acid bound to protein is cleaved by the action of Clostridium perfringens N-acetylneuraminate glycohydrolase (neuraminidase, sialidase) when the purified enzyme is added to the suspenion medium of intact murine melanoma cells freshly derived from the tumor. Cleavage of lipid-bound sialic acid is indifferent to the presence of Ca (2+) in the medium. However, maximum release from protein requires a physiological concentration of this divalent cation. Variation in ionic strength has no effect on release of sialic acid. These findings show that restricted portion of the bound sialic acid may be released from the intact murine melanama cell by the extracellularly supplied enzyme acting topographically.

Animals↗
PubMed1975

Effects of strong electrolyte upon the activity of Clostridium perfringens sialidase toward sialyllactose and sialoglycolipids.

Clostridium perfringens sialidase was purified by affinity chromatography. Kinetic properties of the enzyme were examined with sialyllactose and with mixed sialoglycolipids (gangliosides) as substrates. With the latter substrate in 0.01 M Tris-acete in the absence of strong electrolyte, the pH optimum for enzymatic activity was 6.8. Addition of strong electrolyte (0.01 to 0.10 M Nac1) to the reaction medium caused an acidic shift and a broadening of the pH optimum, Enzymatic activity at pH 5.8 rose approximately 2.5-fold; a concomitant loss of activity at pH 6.8 was also observed. The alteration of enzymatic activity caused by strong electrolyte were dependent upon changes in Vmax. Km remained nearly invariant. Thus, a reversible transition of the enzyme from a relatively inactive to a highly active form occurred as a function of strong electrolyte concentration. Determination of the pK values of the active functional groups of C. perfringens sialidase revealed that the effects of strong electrolyte were exerted upon the pKa group of the enzyme. Strong electrolyte appeared to shield unfavorable electrostatic interactions between polyanionic sialoglycolipid micelles and the enzyme molecule, thus protecting the pKa group from inactivation. In comparision with the effects of strong electrolyte upon enzymatic activity toward the sialoglycolipid substrate, those observed with the monovalent substrate, sialyllacthose, were minor. Collectively, these findings indicate that ionic environment may effectively control the activity and relative substrate specificity of C. perfringens sialidase at a given pH. Furthermore, they explain the low pH optima and skewed pH profiles previously reported for enzymatic activity toward high molecular weight substrates.

Clostridium perfringens↗
PubMed1975

Metabolism of glucosyl [13H]ceramide by human skin fibroblasts from normal and glucosylceramidotic subjects.

Metabolic utilization of glucosyl [3H]ceramide (glucocerebroside) by human skin fibroblasts from normal and glucosylceramidotic subjects was examined in cell culture. Exogenous glucosyl [3H]ceramide in the culture medium did not influence activity of "acid" beta glucosidase in either cell type. Expectedly in the lipidotic cells, the enzymatic activity was markedly (similar to 20-fold) lower. Normal cells were found preferentially to utilize exogenous tritium-labeled glucosylceramide for a source of precursors for phopholipid biosynthesis. The fatty acid and the sphingosine components of sphingomyelin, and the fatty acid components of phosphatidylcholine and phosphatidylethanolamine, but not phosphatidylserine and phosphatidylinositol, were tritium-labeled. In contrast, glucosylceramidotic cells utilized labeled glucosylceramide far more for synthesis of lactosylceramide (lactocerebroside) and also higher neutral glycosphingolipid homologues. These experimental findings suggest that glucosyl [3H]ceramide is hydrolyzed in normal skin fibroblasts to [3H]ceramide and further to [3H]dihydrosphingosine and 3H-labeled fatty acids. These compounds are subsequently incorporated into cellular phospholipids. Flux of glucosyl [3H]ceramide through this catabolic sequence and reincorporation of its breakdown products into phospholipids predominates in normal skin fibroblasts. In contrast, it is greatly reduced in glucosylceramidotic skin fibroblasts. Consequently, a greater amount of glucosyl [3H]ceramide remains intact for the synthesis of more highly glycosylated glycosphingolipids in the latter cells.

Cells, Cultured↗
PubMedDate not supplied

Liver biopsies in patients with lysosomal storage disease: experience with effective sedation.

We prospectively applied a protocol used to sedate children who required a liver biopsy. Sixty liver biopsies were performed on thirty pediatric patients to assess the effects of treatment. Sixteen patients had Type 1 Gaucher's disease of which seven had a platelet count between 50-100,000/mm3. All seven had bleeding time performed and when indicated, intravenous DDAVP (1-deamino-8-D-arginine vasopressin) was used to improve hemostasis. Fourteen patients had Niemann-Pick disease type C of which eight were significantly demented and uncooperative. Before liver biopsy, all patients were sedated with the following regimen: oral chlorpromazine (1 mg/kg) followed one hour later by intravenous meperidine (1 mg/kg) and pentobarbital (maximum dosage 6 mg/kg) administered by slow intravenous injection. Liver biopsies were obtained safely on all patients. Only 1 patient (2%) developed a potentially serious complication: an obstructed airway which was readily corrected by simple repositioning. Transient less serious complications occurred in another 7 patients (12%). There was no long term sequalae of the biopsy procedures. Our study indicates that with appropriate patient selection, this sedation protocol may be useful in pediatric patients requiring a liver biopsy.

Adolescent↗
PubMedDate not supplied

MRI of multiple platyspondyly in Gaucher disease: response to enzyme replacement therapy.

Vertebra plana and multiple platyspondyly are complications of aggressive Gaucher disease. Magnetic resonance imaging readily identifies vertebra plana and secondary spinal cord compression. We present a case of a 2-year-old boy with clinically aggressive Type 1 Gaucher disease in whom MRI showed partial reconstitution of the height of a collapsed lumbar vertebral body after 16 months of enzyme replacement therapy.

Child, Preschool↗