THE DIGESTION AND INACTIVATION OF MALTASE BY TRYPSIN AND THE SPECIFICITY OF MALTASES

1. The maltase of saliva and that of E. coli (B. coli communis) hydrolyze maltose but not α-methylglucoside or sucrose and are therefore to be considered glucomaltases. 2. Maltase is rapidly and completely inactivated and digested by trypsin.     

School achievement in children with hypothyroidism detected at birth and search for predictive factors.

Neonatal screening of hypothyroidism started in 1975, and now sufficient hindsight is gained to assess school results in children with hypothyroidism and compare them to IQ tests. From the 85 cases of hypothyroidism detected in the Midi-Pyrénées area, 40 have enrolled in or finished primary school and 18 started secondary school. School achievement was assessed by school test results in French and mathematics using specific grids for each class and by retention rates. These results were compared to control groups. The hypothyroid group obtained identical results in French to those of the control groups but scored lower in mathematics. Grade retention rated higher in hypothyroid children (20%) than in the control groups (12.5%), especially in the first primary school grade. The search for predictive severity factors revealed significant differences between the grade repeater group and the nonrepeater group: more cases of athyrosis (75 vs. 25% for ectopia), lower T4 levels at birth, lower bone surface, lower IQ at 4 and 7 years, neurological troubles of fine motricity and coordination, and lower socioeconomic level. These results should shortly be taken into consideration in order to isolate a group at risk and undertake specialized care to improve school results in this group.     

Incorporation of non-acetylated hexosamines into plasma membrane glycoproteins of liver cells after galactosamine injection

The following procedure for the detection of non-acetylated amino sugars in the plasma membrane was established: i) derivatization of free amino groups with dansyl-chloride, ii) hydrolysis with 3 M HCl (for 4 h at 105 degrees C) to liberate the dansylated carbohydrate moieties from the plasma membrane, iii) purification of the dansylated amino sugars by paper chromatography and subsequent analysis by thin-layer chromatography. Using this procedure, plasma membranes from rat liver were analysed after injection of D-[14C]galactosamine. For this purpose, rats were divided into three groups: the first received D-galactosamine.HCl at a dose of 2 mg/kg b.w., the second at a dose of 75 mg/kg b.w. and the third at a hepatitis-inducing dose of 260 mg/kg b.w.. In all three groups the majority of the protein-bound radioactivity in the plasma membrane was not dansylated, thus representing N-acetylated amino sugars. At a dose of 2 mg/kg, only 0.34% of the protein-bound radioactivity in the plasma membrane reacted with dansyl-chloride. At a dose of 70 mg/kg this value increased to 1.9%. At 260 mg/kg the value was 3.6%. These results indicate that the incorporation of non-acetylated amino sugar into the plasma membrane was dose-dependent and reached 90 pmol per mg plasma membrane protein during galactosamine injury. However, this incorporation of non-acetylated amino sugars into the plasma membrane did not represent a pathological mechanism responsible for the onset of the galactosamine-induced liver injury.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lectin specificity and binding characteristics of human C-reactive protein.

C-reactive protein (CRP) is thought to play an important role in immunomodulation. The exact biologic function of this pentraxin protein is, however, still unclear. Here we report experiments designed to further characterize the binding properties of CRP. Using purified human CRP it could be shown that CRP immobilized onto polystyrene surfaces or onto latex beads binds distinct plasma glycoproteins including IgG, asialofetuin, asialo-beta 2-glycoprotein I and, likewise, synthetic glycoproteins as a lectin, exhibiting binding specificity for terminal galactosyl residues of the glycoprotein glycans. Binding of CRP to IgA, IgM, IgG, asialofetuin, asialo-beta 2-glycoprotein I and to synthetic glycoproteins requires immobilization onto surfaces of both CRP and the ligand. Fibronectin and fibrinogen are bound by surface-immobilized CRP also in soluble phase. Comparing various mono-, di-, and trisaccharides as competitive inhibitors of the lectin binding activity of CRP, only beta-D-Gal-(1-3)-D-GalNAc, beta-D-Gal-(1-4)-D-GalNAc, and beta-D-Gal-(1-4)-beta-D-Gal-(1-4)-D-GlcNAc had significant inhibitory power at a concentration of 8 mmol/liter. Binding activity of CRP was pH-dependent with an optimum at pH 5 to 6 and was reduced by 90% when pH was shifted from 6 to the physiologic pH value of 7.4. CRP exhibited lectin-like properties with binding specificity for galactosyl residues also when bound to K-562 erythroleukemia cells. It is therefore suggested that CRP immobilized onto surfaces exhibits lectin activity toward galactosyl groups preferentially in a mildly acidic environment as present at sites of inflammation.