Down syndrome with duplication of a region of chromosome 21 containing the CuZn superoxide dismutase gene without detectable karyotypic abnormality

Summary We report the case of an 18-month-old boy with many typical Down syndrome features but a normal cytogenetic analysis. High-resolution banding techniques on lymphocytes and fibroblasts of the propositus and his parents did not show any detectable abnormality including that of trisomy 21 mosaicism. However, CuZn superoxide dismutase (CuZn SOD) in the patient's red cells was increased as in trisomy 21. DNA analysis (Southern blots) using a human CuZn SOD probe showed that the genotype of the propositus contained three CuZn SOD genes. In situ hybridization on metaphase chromosomes with the same probe confirmed the gene location in a segment enclosing the distal part of 21q21 and 21q22.1. There was no significant labeling on other chromosomes of the patient. These results indicate that the Down syndrome phenotype of this patient is due to microduplication of a chromosome 21 fragment containing the CuZn SOD gene.     

Endogenous production of prothymocyte differentiating activity by phytohemagglutinin-stimulated T-cell-depleted human marrow

The PHA responsiveness of marrow T-cell precursors remains a matter of controversy. We have investigated the capacity of human marrow to proliferate under phytohemagglutinin (PHA) stimulation following extensive removal of mature T cells by complement-dependent cytotoxicity with MBG6 and RFT8 monoclonal antibodies. PHA-induced thymidine uptake by marrow cells occurred with a peak on Days 6-8 of incubation instead of Day 3 for PBL. This peak was observed 48 hr earlier in the presence of PHA-stimulated T-depleted marrow cell supernatants. These supernatants can also promote the growth of mature T-cell colonies from MBG6-, RFT8-, T11-, T3- marrow. However, full colony development requires exogenous interleukin 2 (IL-2). IL-2 could be detected in marrow supernatants but only at very low levels and beyond Days 3 and 4. In contrast Days 1-6 marrow supernatants were equally effective in promoting MBG6-RFT8- marrow cell responsiveness to PHA. We conclude that marrow T-cell precursors are not PHA responsive and that PHA induces the production by marrow non-T cells of a prothymocyte-differentiating activity (PTDA); PTDA can differentiate marrow T-cell progenitors into PHA-responsive T cells; following activation by PHA, these cells undergo limited proliferation induced by IL-2 endogenously released from de novo differentiated T cells. It is suggested that this mechanism may account for extrathymic differentiation of the T-cell lineage in heavily irradiated marrow transplantation recipients.     

Fibronectin glycosylation modulates fibroblast adhesion and spreading

The role of the carbohydrate residues of fibronectin concerning the specificities of that glycoprotein to interact with fibroblastic cell surfaces, gelatin, and heparin was examined. Tunicamycin was used to produce carbohydrate-depleted fibronectin; it was synthesized by cultured fibroblasts. Unglycosylated and glycosylated fibronectins were analyzed for their ability to bind gelatin and heparin, using affinity columns. Fibronectin-coated surfaces were used to quantitatively measure cell adhesion and spreading. The results showed that the lack of carbohydrates significantly increased the interaction of the protein with gelatin and markedly enhanced its ability to promote adhesion and spreading of fibroblasts. In contrast, the binding of fibronectin to heparin was not influenced by glycosylation. The composite data indicate that the Asn-linked oligosaccharides of fibronectin act as modulators of biological functions of the glycoprotein.     

Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

Inhibition of the NADH oxidase activity of plasma membranes isolated from xenografts and cell lines by the antitumor sulfonylurea,N-(4-methylphenylsulfonyl)-N′-(4-chlorophenyl)urea (LY 181984) correlates with drug susceptibility of growth

Summary Inhibition of NADH oxidase activity of plasma membranes isolated from a series of human xenografts and cell lines by the antitumor sulfonylurea, N-(4-methylphenylsulfonyl)-N-(4-chlorophenyl) urea (LY 181984), correlated with the ability of the sulfonylurea to inhibit cell growth. Growth of rat kidney cells either untransformed or transformed with Kirsten-ras (K-ras) were unaffected by the sulfonylurea. Similarly, the NADH oxidase activity of isolated plasma membranes from K-ras transformed cells was unaffected by LY 181984. In contrast, when transformed with Harvey-ras (H-ras), both growth and NADH oxidase activity were inhibited. With the inactive but structurally related LY 181985 (N-4-methylphenyl-sulfonyl)-N-(phenyl)urea), neither growth nor plasma membrane NADH oxidase activity of either sulfonylurea-susceptible or -resistant tissues or cell lines was inhibited. Both sulfonylureas were inactive with rat liver plasma membranes but NADH oxidase activity of plasma membranes and growth with HeLa cells was inhibited by the active (LY 181984) but not by the inactive (LY 181985) sulfonylurea. The findings suggest a possible correlation between inhibition of plasma membrane NADH oxidase activity by the antitumor sulfonylureas and their oncolytic action.