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N C Phillips

Publications and source records attributed to N C Phillips.

67 records · Page 4Linked to original sources
PubMed1978

Lysosomal glycosidase activities in human hair roots.

The levels of three lysosomal glycosidase, alpha-D-mannosidase, a-L-fucosidase and beta-D-hexosaminidase have been determined in normal hair roots and in hair roots obtained from a patient with mannosidosis. The most active glycosidase in normal hair roots was beta-D-hexosaminidase, followed by alpha-L-fucosidase and alpha-D-mannosidase. There was no alpha-D-mannosidase activity in the hair roots of the patient with mannosidosis. The significance of these results is discussed in relation to the detection of lysosomal storage diseases.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1977

A serological investigation into the acidic alpha-D-mannosidase in normal Angus cattle and in a calf with mannosidosis.

Antiserum was raised in a rabbit against bovine kidney acidic alpha-mannosidase that had been purified 570-fold by affinity chromatography on concanavalin A--Sepharose and Sepharose 4B-xi-aminohexanoylmannosylamine. The antiserum precipitated the acidic but not the neutral alpha-mannosidase in normal calf tissues. Human acidic alpha-mannosidase cross-reacted partially with the antiserum, emphasizing the close structural resemblance between the enzyme in the two species. The residual acidic alpha-mannosidase in the tissues of a calf with mannosidosis was also precipitated by the antiserum, the same volume of antiserum being required to precipitate a unit of alpha-mannosidase activity from the normal and pathological tissues. The concentration of cross-reacting material detected by antibody-consumption experiments in the organs of the calf with mannosidosis appeared to be proportional to the concentration of the residual acidic alpha-mannosidase. It is suggested that the residual acidic alpha-mannosidase in mannosidosis accounts for the cross-reacting material detected and that it is unlikely that enzymically inactive but cross-reacting material is present. The residual acidic alpha-mannosidase could be a decreased concentration of the normal gene product or an altered enzyme with a decreased specific enzymic activity and a correspondingly decreased antigenicity.

Animals↗
PubMed1976

Characterization of human liver alpha-D-mannosidase purified by affinity chromatography.

Human liver acidic alpha-D-mannosidase was purified 1400-fold by a relatively short procedure incorporating chromatography on concanavalin A-Sepharose and affinity chromatography on Sepharose 4B-epsilon-aminohexanoylmannosylamine. In contrast with the acidic enzymic activity the neutral alpha-mannosidase did not bind to the concanavalin A-Sepharose so the two types of alpha-mannosidase could be separated at an early stage in the purification. The only significant glycosidase contaminant after affinity chromatography on the mannosylamine ligand was alpha-L-fucosidase, which was selectively removed by affinity chromatography on the corresponding fucosylamine ligand. The final preparation was free of other glycosidase activities. The pI of the purified enzyme was increased from 6.0 to 6.45 on treatment with neuraminidase. Although the pI and the mol.wt. (220 000) suggested that alpha-mannosidase A had been purified selectively, ion-exchange chromatography on DEAE-cellulose indicated that the preparation consisted predominantly of alpha-mannosidase B. This discrepancy is discussed in relation to the basis of the multiple forms of human alpha-mannosidase. The purified enzyme completely removed the alpha-linked non-reducing terminal mannose from a trisaccharide isolated from the urine of a patient with mannosidosis. A comparison of the activity of the pure enzyme towards the natural substrate and synthetic substrates suggests that the same enzymic activity is responsible for hydrolysing all the substrates. These results validate the use of synthetic substrates for determining the mannosidosis genotype. They are also further evidence that mannosidosis is a lysosomal storage disease resulting from a deficiency of acidic alpha-mannosidase.

Disaccharidases↗
PubMed1974

Mannosidosis in Angus cattle. The enzymic defect.

Normal calf alpha-mannosidase activity exists in at least three forms separable by chromatography on DEAE-cellulose and by starch-gel electrophoresis. Two components, A and B, have optimum activity between pH3.75 and 4.75, but component C has an optimum of pH6.6. Components A and B are virtually absent from the tissues of a calf with mannosidosis and the residual activity is due to component C. The acidic and neutral forms of alpha-mannosidase differ in their molecular weights and sensitivity to EDTA, Zn(2+), Co(2+) and Mn(2+). An acidic alpha-mannosidase component (pH optimum 4.0) accounts for most of the activity in normal plasma but it is absent from the plasma of a calf with mannosidosis. Although the acidic alpha-mannosidase component is probably related to tissue components A and B, it can be distinguished from them by ion-exchange chromatography and gel filtration. The optimum pH of the low residual activity in the plasma from a calf with mannosidosis is pH5.5-5.75. The results support the hypothesis that Angus-cattle mannosidosis is a storage disease caused by a deficiency of lysosomal acidic alpha-mannosidase activity.

Animals↗
PubMedDate not supplied

Activation of murine Kupffer cell tumoricidal activity by liposomes containing lipophilic muramyl dipeptide.

The ability of liposomes containing a lipophilic muramyl dipeptide, N-acetylmuramyl-L-alanyl-D-isoglutamine-glycerol dipalmitate, to induce Kupffer cell tumoricidal activity has been investigated. Liposomal N-acetylmuramyl-L-alanyl-D-isoglutamine-glycerol dipalmitate was 16-fold more potent than liposomal N-acetylmuramyl-L-alanyl-D-isoglutamine and 2,400-fold more potent than N-acetylmuramyl-L-alanyl-D-isoglutamine in inducing Kupffer cell tumoricidal activity in vitro. A single i.v. injection of liposomes containing N-acetylmuramyl-L-alanyl-D-isoglutamine-glycerol dipalmitate was capable of inducing Kupffer cell tumoricidal activity as measured against B16-melanoma cells after Kupffer cell isolation. Maximal cytotoxic activity was obtained with 1 microgram muramyl dipeptide-glycerol dipalmitate encapsulated within liposomes: doses of 10 or 100 micrograms inhibited tumoricidal activity. Kupffer cells from mice treated with liposomes containing N-acetylmuramyl-L-alanyl-D-isoglutamine-glycerol dipalmitate remained cytotoxic for at least 6 days after injection. Liposomal N-acetylmuramyl-L-alanyl-D-isoglutamine was significantly less potent than liposomal N-acetylmuramyl-L-alanyl-D-isoglutamine-glycerol dipalmitate in inducing Kupffer cell tumoricidal activity in situ. N-Acetylmuramyl-L-alanyl-D-isoglutamine was capable of inducing Kupffer cell tumoricidal activity in vitro: its failure to induce tumoricidal activity in situ at doses of 1,000 micrograms demonstrates the utility of liposomal carriers for the in vivo activation of Kupffer cells by muramyl dipeptides.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMedDate not supplied

Correction of defective tumoricidal activity of macrophages from A/J mice by liposomal immunomodulators.

The ability of liposomal immunomodulators to restore abnormal macrophage tumoricidal activity has been studied. Macrophages from A/J mice have impaired responses in vitro to macrophage activating factor, gamma-interferon, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) or lipopolysaccharide when compared with macrophages from normoresponsive C57BL/6J mice. Liposomes containing a lipophilic muramyl dipeptide MDP-glyceroyl dipalmitate, macrophage activating factor or gamma-interferon restored tumoricidal activity to levels similar to C57BL/6J macrophages. Pretreatment of A/J mice with Corynebacterium parvum resulted in low levels of macrophage tumoricidal activity: treatment of C. parvum-induced A/J macrophages in vivo or in vitro with liposomal MDP-glyceroyl dipalmitate or liposomal macrophage activating factor resulted in normal levels of cytotoxicity. Macrophages from A/J mice were unable to phagocytose liposomes in vitro as rapidly or to the same extent as macrophages from C57BL/6J mice. The levels of cytotoxicity observed indicate that this is not a limiting factor for the induction of tumoricidal activity by liposomal immunomodulators.

Adjuvants, Immunologic↗
PubMedDate not supplied

Drug retention and stability of solid lipid nanoparticles containing azidothymidine palmitate after autoclaving, storage and lyophilization.

Solid lipid nanoparticles (SLNs) were prepared using trilaurine (TL) as the SLN core and phospholipid (PL) as coating. Neutral and negatively charged PLs were used to produce neutral and negatively charged SLNs. An ester prodrug of 3'-azido-3'-deoxythymidine (Zidovudine, AZT), AZT palmitate (AZT-P), was synthesized and incorporated in the SLNs. The stability of SLN formulations containing AZT-P was studied at different temperatures. Drug retention and mean particle diameter of SLNs were determined after autoclaving, during temperature stability testing, and after lyophilization (with or without cryoprotective sugars) and reconstitution. There were no significant changes in the mean diameter and the zeta potential (zeta) of SLNs after autoclaving (121 degrees C for 20 min). The amount of incorporated AZT-P was, however, slightly reduced due to the formation of hydrosoluble AZT. Autoclaved SLNs were stable for a period of 10 weeks at 20 degrees C but an increase in particle size and loss of AZT-P were observed at 4 and 37 degrees C. Trehalose was an effective cryoprotectant for preventing SLN aggregation during lyophilization and subsequent reconstitution. Thermal gravimetric analysis showed that lyophilized preparations contained approximately 1% water. Using appropriate trehalose to lipid ratios, AZT-P retention in the SLNs was 100% after reconstitution. Our results demonstrate that SLNs containing AZT-P can be autoclaved, lyophilized and reconstituted without significant changes in SLN diameter and zeta potential or in the quantity of incorporated prodrug.

Calorimetry, Differential Scanning↗
PubMedDate not supplied

Review of etoposide.

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Animals↗