Expression of GDP-L-Fuc: Gal(beta 1-4)GlcNAc-R (Fuc to GlcNAc) alpha-1,3-fucosyltransferase and its relationship to glycoprotein structure in a human erythroleukemia cell line, HEL.

Terminal glycosylation may be a mechanism to control the function of specific biologically active glycoproteins. The biosynthesis of terminal sialyl and fucosyl residues on certain glycoproteins has been linked to the expression of the respective glycosyltransferase. In contrast, a human erythroleukemia cell line, HEL, contained a highly active GDP-L-Fuc: Gal(beta 1-4)GlcNAc-R (Fuc to GlcNAc) alpha-1,3-fucosyltransferase (alpha-1,3-fucosyltransferase) but no detectable alpha-1,3-linked fucosyl residues on the glycoproteins. The alpha-1,3-fucosyltransferase gave apparent Km values for Fuc(alpha 1-2)Gal(beta 1-4)GlcNAc beta-O-benzyl, Gal(beta 1-4)GlcNAc and GDP-fucose of 0.04, 0.68 and 0.12 mM, respectively. The lack of detectable fucosyl residues in alpha-1,3-linkage to GlcNAc on the [3H]fucose-labeled glycoproteins was shown with the use of almond alpha-1,3/4-fucosidase and internal controls to verify that the enzyme was active. Using Western-blot analysis, HEL cell glycoproteins reacted with blood group H type-2 antibody, confirming the presence of Fuc(alpha 1-2)Gal(beta 1-4)GlcNAc as reported by others and the presence of the preferred substrate for the enzyme. It is proposed that controls for terminal glycosylation in addition to glycosyltransferase expression are operative in HEL cells and that they are part of a multi-regulated process controlling terminal modifications of glycoproteins.

Purification and characterization of GDP-L-Fuc-N-acetyl-beta-D-glucosaminide alpha 1----3fucosyltransferase from human neuroblastoma cells. Unusual substrate specificities of the tumor enzyme.

Fucosyl residues in the alpha 1----3 linkage to N-acetylglucosamine (Fuc alpha 1----3GlcNAc) on oligosaccharides of glycoproteins and glycolipids have been detected in certain human tumors and are developmentally expressed (reviewed in Foster, C. S., and Glick, M. C. (1988) Adv. Neuroblastoma Res. 2, 421-432). In order to understand control mechanisms for the biosynthesis of these fucosylated glycoconjugates, GDP-L-Fuc-N-acetyl-beta-D-glucosaminide alpha 1----3fucosyltransferase was purified from human neuroblastoma cells, CHP 134, utilizing either the immobilized oligosaccharide or disaccharide substrates. The enzyme, extracted from CHP 134 cells, was purified by DEAE- and SP-Sephadex chromatography and then by either immobilized substrate. alpha 1----3Fucosyltransferase was obtained in approximately 10% yield and was purified 45,000-fold from the cell extract. The kinetic properties of the enzyme showed an apparent KGDP-Fuc 43 microM, KGal beta 1----4GlcNAc 0.4 mM, KGal beta 1----4Glc 8.1 mM, and KFuc alpha 1----2Gal beta 1----4Glc 1.0 mM. Polyacrylamide gel electrophoresis of the affinity-purified enzyme showed two proteins which migrated, Mr = 45,000-40,000. The enzyme differed in substrate specificity, pH optimum, response to N-ethylmaleimide and ion requirements from the enzymes purified from human milk or serum. The inability of alpha 1----3fucosyltransferase to transfer to substrates containing NeuAc alpha 2----3 or alpha 2----6Gal is in contrast to the reports for the enzyme in other human tumors. This substrate specificity correlates with the oligosaccharide residues thus far defined on glycoproteins of CHP 134 cells since NeuAc and Fuc alpha 1----3GlcNAc have yet to be detected on the same oligosaccharide antenna. However, the enzyme transfers to Fuc alpha 1----2Gal beta 1----4GlcNAc/Glc with higher activity than the unfucosylated disaccharides, although neither alpha 1----2fucosyltransferase nor Fuc alpha 1----2 residues have been detected in CHP 134 cells. The different substrate specificities of alpha 1----3fucosyltransferase isolated from human tumors and normal sources leads to the suggestion that a family of alpha 1----3fucosyltransferases may exist and that they may be differentially expressed in human tumors.

Neonatal infection in premature infants and use of human immunoglobulin.

In an open study 120 consecutively admitted premature babies of 32 weeks' gestation or less, were randomised to receive weekly intramuscular injections of human normal immunoglobulin (50 mg/kg). There was no significant difference between the number of babies in the treated and untreated groups who had at least one episode of infection, but the total number of infective episodes was substantially less in the treated group (n = 22) compared with 40 in the non-treated group. Three babies died from overwhelming infection and three babies developed necrotising enterocolitis, all in the group that had not been treated. Serum IgG concentrations were significantly higher in the treated group by the age of 2 weeks but remained consistently below those of full term babies of similar postnatal age. Administration of human immunoglobulin may decrease the severity of infection in premature babies, but alternative regimens may be more successful.

Controlled trial of house dust mite avoidance in children with mild to moderate asthma.

Twenty-six asthmatic children participated in a controlled trial of house dust mite avoidance. Group A (n = 14) had 12 weeks' avoidance, provided that they had not deteriorated at the end of the first 6 weeks. Group B (n = 12) had an initial 6 weeks' observation period followed by 6 weeks' avoidance. Mite numbers were extremely variable and often low. There was a significant fall in mite numbers in the first, but not the second, 6-week period in group A. In group B there was a significant fall in mite numbers in both the first (observation) and second (active avoidance) periods. Active avoidance produced highly significant falls in total serum IgE. There were no significant changes in IgE during the observation period. This impressive immunological effect was not associated with any changes in the radio-allergo-sorbent assay (RAST) to house dust mite, or symptom scores; peak expiratory flow rates or histamine induced bronchial reactivity. More rigorous avoidance procedures in more severely affected asthmatic patients warrants further investigation.

Rubinstein-Taybi syndrome: further evidence of a genetic aetiology.

Two families are described with Rubinstein-Taybi syndrome. In one family the syndrome is seen in its full form in the index case and his uncle; three cousins of the index case also show varying degrees of expression of the disorder. In the other family a brother and sister are affected. This case report illustrates the varying expression of the disorder and the change in facial appearance with age. A polygenic basis of inheritance is supported and it is suggested that the typical facial appearance in infancy is the best means of identifying the disorder, as broad thumbs and toes may not be apparent or may be only a borderline abnormality.

Analysis of ethnic influence on stillbirths and infant mortality in Bradford 1975-81.

The patterns of mortality from birth to 1 year in Bradford were studied in the seven year period 1975-81. Large differences in mortality between the Asian and non-Asian population were shown. In 1981 77% of Bradford Asian families were of Pakistani origin, the remaining 23% consisting of families from other parts of the Indian subcontinent and a few from East Africa. There were excess mortality with associated congenital abnormality in the Asian population. From 1975 to 1981 there were 133 deaths associated with congenital abnormality (a rate of 12.4 per 1000 total births) in the Asian population compared with a figure of 129 (4.8 per 1000) in the non-Asian population. The differences between the two groups are shown to be largely independent of social class, and other possible reasons for the discrepancy between the Asian and non-Asian populations are discussed.

Vitamin B12 neuropathy in a 6 year old.

Gross neuropathy consequent upon selective malabsorption of vitamin B12 was diagnosed in a 6 year old Bangladeshi girl brought to Great Britain for further investigation of an unexplained illness of three years' duration. The initial peripheral blood count was normal. Treatment with vitamin B12 has led to substantial recovery.

Effect of phototherapy on plasma 25(OH)-vitamin D in neonates.

The possibility that phototherapy may increase plasma levels of 25(OH)-vitamin D was assessed by measuring levels before and after 48 h continuous phototherapy using a standard phototherapy unit (Vickers, Basingstoke , England). There was no significant increase in plasma 25(OH)-vitamin D after 48 h phototherapy and it is concluded that such treatment does not stimulate photobiosynthesis of vitamin D.

Cystic fibrosis presenting with chronic electrolyte depletion, metabolic alkalosis and hyperaldosteronism.

A five month old infant who presented with failure to thrive and was found to have severe electrolyte depletion, metabolic alkalosis and hyperaldosteronism is described. The diagnosis of cystic fibrosis was made by demonstrating abnormal sweat electrolytes and pancreatic insufficiency. It is important to exclude cystic fibrosis in any infant presenting with this biochemical abnormality.