An experimental procedure for the measurement of the ganglioside radioactivity labelled in vivo.
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Animals↗
Biomedical subjects
G C Chen
Publications and source records attributed to G C Chen.
Brain ceramide hexosides in Tay-Sachs disease and generalized gangliosidosis (GM1-gangliosidosis).
The carbohydrate composition was determined for ceramide hexosides isolated from brains of patients with Tay-Sachs disease and generalized gangliosidosis (hereby named GM1-gangliosidosis). Gray matter of patients with each disease showed a characteristic abnormal ceramide hexoside pattern. In Tay-Sachs gray matter, ceramide trihexoside is the major component, whereas ceramide tetrahexoside is barely detectable. In GM1-gangliosidosis, ceramide tetrahexoside is the major ceramide hexoside, while ceramide trihexoside is present only in small amount. These two major components have been characterized as the asialo derivatives of, respectively, the "Tay-Sachs ganglioside" (GM2-ganglioside) and the normal major monosialoganglioside (GM1-ganglioside). In both diseases, more than half the ceramide monohexoside of gray matter was glucocerebroside. Gray matter ceramide dihexoside, present in both diseases at higher than normal levels, was mostly ceramide lactoside, with possibly a small amount of ceramide digalactoside. Sulfatide contained only galactose. The abnormal ceramide hexoside pattern is limited to gray matter: white matter showed normal ceramide hexosides, i.e. a preponderance of monohexosides and sulfatide, with no detectable glucocerebroside.
Brain Chemistry↗
Pre-beta high density lipoprotein. Unique disposition of apolipoprotein A-I increases susceptibility to proteolysis.
Apolipoprotein A-I-containing lipoproteins (high density lipoproteins, HDL) can be separated into two subfractions, which have pre-beta and alpha electrophoretic mobilities, respectively. These fractions differ in both composition and structure. Some preparations of pre-beta-migrating HDL, but not alpha-migrating HDL, were found to contain two polypeptides with Mr of approximately 26 and 14 kDa, which are scission products of apolipoprotein (apo) A-I. They are recognized by monospecific antibodies to apo A-I and have N-terminal sequences identical to those of mature apo A-I. This proteolytic scission of apo A-I occurs primarily after venipuncture. Immediate addition of protease inhibitors minimized the appearance of the fragments in plasma. To study the relative susceptibilities of pre-beta and alpha HDL to proteolysis, the lipoproteins were incubated in vitro with plasmin. The apo A-I in pre-beta HDL was extensively degraded, but that in alpha-migrating HDL was degraded to a much lesser extent, indicating that the appearance of apo A-I fragments in pre-beta HDL was due to enhanced sensitivity to proteolysis. To varying degrees, thrombin, kallikrein, elastase, arginine C endoprotease, and chymotrypsin also appear to cleave pre-beta HDL faster than alpha HDL. Most of the proteases generated a 12 to 14 kDa peptide fragment under conditions of limited cleavage. These results suggest that the conformational state of apo A-I in pre-beta-migrating HDL or its spatial relationship to lipids is significantly different from that of apo A-I in alpha-migrating HDL.(ABSTRACT TRUNCATED AT 250 WORDS)
Apolipoprotein A-I↗
Remnants of lipoproteins of intestinal and hepatic origin in familial dysbetalipoproteinemia.
We used the low molecular weight form of apolipoprotein B (B-48) as a marker for the identification of remnant particles formed from chylomicrons in the plasma of patients with familial dysbetalipoproteinemia. In the serum of patients fasted 14 hours, the d less than 1.006 g/cm3 lipoproteins of prebeta mobility, separated by starch block electrophoresis, contained only the primary hepatogenous species of apolipoprotein B (B-100), and their lipid composition resembled that of normal prebeta very low density lipoproteins. In contrast, the fraction with beta mobility contained both the B-48 and B-100 proteins; the B-48 protein was found primarily among the largest particles. All fractions of beta mobility were greatly enriched with cholesteryl esters. The beta fraction thus contains remnant particles which appear to originate both from chylomicrons and hepatogenous very low density lipoproteins. It appears that these remnant particles share a common removal mechanism which is impaired in familial dysbetalipoproteinemia.
Adult↗
Adsorption-desorption behavior of copper at contaminated levels in red soils from China.
Adsorption-desorption of copper (Cu2+) at contaminated levels in two red soils was investigated. The red soil derived from the Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult) (REQ) adsorbed more Cu2+ than the red soil developed on the Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept) (RAR). The maximum adsorption values (M(A)) that are obtained from the simple Langmuir model were 25.90 and 20.17 mmol Cu2+ kg(-1) soil, respectively, for REQ and RAR. Adsorption of Cu2+ decreased soil pH, by 0.8 unit for the REQ soil and 0.6 unit for the RAR soil at the highest loadings. The number of protons released per Cu2+ adsorbed increased sigmoidally with increasing initial Cu2+ concentration for the RAR soil, but the relationship was almost linear for the REQ soil. The RAR soil released about 2.57 moles of proton per mole of Cu2+ adsorbed at the highest Cu2+ loading and the corresponding value for the REQ soil was 1.12. The distribution coefficient (Kd) decreased exponentially with increasing Cu2+ loading. Most of the adsorbed Cu2+ in the soils was readily desorbed in the NH4Ac. After five successive extractions with 1 mol L(-1) NH4Ac (p 5.0), 61 to 95% of the total adsorbed Cu2+ in the RAR soil was desorbed and the corresponding value for the REQ soil was 85 to 92%, indicating that the RAR soil had a greater affinity for Cu2+ than the REQ soil at low levels of adsorbed Cu2+.
Adsorption↗