Heritability of adult body height: a comparative study of twin cohorts in eight countries.

A major component of variation in body height is due to genetic differences, but environmental factors have a substantial contributory effect. In this study we aimed to analyse whether the genetic architecture of body height varies between affluent western societies. We analysed twin data from eight countries comprising 30,111 complete twin pairs by using the univariate genetic model of the Mx statistical package. Body height and zygosity were self-reported in seven populations and measured directly in one population. We found that there was substantial variation in mean body height between countries; body height was least in Italy (177 cm in men and 163 cm in women) and greatest in the Netherlands (184 cm and 171 cm, respectively). In men there was no corresponding variation in heritability of body height, heritability estimates ranging from 0.87 to 0.93 in populations under an additive genes/unique environment (AE) model. Among women the heritability estimates were generally lower than among men with greater variation between countries, ranging from 0.68 to 0.84 when an additive genes/shared environment/unique environment (ACE) model was used. In four populations where an AE model fit equally well or better, heritability ranged from 0.89 to 0.93. This difference between the sexes was mainly due to the effect of the shared environmental component of variance, which appears to be more important among women than among men in our study populations. Our results indicate that, in general, there are only minor differences in the genetic architecture of height between affluent Caucasian populations, especially among men.     

Replication of macrophage-tropic and T-cell-tropic strains of human immunodeficiency virus type 1 is augmented by macrophage-endothelial cell contact.

Macrophages perform a central role in the pathogenesis of human immunodeficiency virus type 1 (HIV-1) infection and have been implicated as the cell type most prominent in the development of central nervous system impairment. In this study, we evaluated the effect of interaction between macrophages and endothelial cells on HIV-1 replication. Upregulation of HIV-1 replication was consistently observed in monocyte-derived macrophages (hereafter called macrophages) cocultured with either umbilical vein endothelial cells or brain microvascular endothelial cells. HIV-1 p24 antigen production of laboratory-adapted strains and patient-derived isolates was increased 2- to 1,000-fold in macrophage-endothelial cocultures, with little or no detectable replication in cultures containing endothelial cells only. The upregulation of HIV-1 in macrophage-endothelial cocultures was observed not only for viruses with the non-syncytium-inducing, macrophage-tropic phenotype but also for viruses previously characterized as syncytium inducing and T-cell tropic. In contrast, cocultures of macrophages with glioblastoma, astrocytoma, cortical neuronal, fibroblast, and placental cells failed to increase HIV-1 replication. Enhancement of HIV-1 replication in macrophage-endothelial cocultures required cell-to-cell contact; conditioned media from endothelial cells or macrophage-endothelial cocultures failed to augment HIV-1 replication in macrophages. Additionally, antibody to leukocyte function-associated antigen (LFA-1), a macrophage-endothelial cell adhesion molecule, inhibited the enhanced HIV-1 replication in macrophage-endothelial cell cocultures. Thus, these data indicate that macrophage-endothelial cell contact enhances HIV-1 replication in macrophages for both macrophage-tropic and previously characterized T-cell-tropic strains and that antibody against LFA-1 can block the necessary cell-to-cell interaction required for the observed upregulation. These findings may have important implications for understanding the ability of HIV-1 to replicate efficiently in tissue macrophages, including those in the brain and at the blood-brain barrier.     

Identification of domains within the human cytomegalovirus major immediate-early 86-kilodalton protein and the retinoblastoma protein required for physical and functional interaction with each other.

The human cytomegalovirus major immediate-early 86-kDa protein (IE2 86) plays an important role in the trans activation and regulation of HCMV gene expression. Previously, we demonstrated that IE2 86 contains three regions (amino acids [aa] 86 to 135, 136 to 290, and 291 to 364) that can independently bind to in vitro-translated Rb when IE2 86 is produced as a glutathione S-transferase fusion protein (M. H. Sommer, A. L. Scully, and D. H. Spector, J. Virol. 68:6223-6231, 1994). In this report, we have elucidated the regions of Rb involved in binding to IE2 86 and have further analyzed the functional nature of the interaction between these two proteins. We find that two domains on Rb, the A/B pocket and the carboxy terminus, can each independently form a complex with IE2 86. In functional assays, we demonstrate that IE2 86 and another IE protein, IE1 72, can counter the enlarged flat cell phenotype, but not the G1/S block, which results from expression of wild-type Rb in the human osteosarcoma cell line Saos-2. Mutational analysis reveals that there are two domains on IE2 86 that can independently affect Rb function. One region (aa 241 to 369) includes the major Rb-binding domain, while the second maps to the amino-terminal region (aa 1 to 85) common to both IE2 86 and IE1 72. These data show that Rb and IE2 86 physically and functionally interact with each other via at least two separate domains and provide further support for the hypothesis that IE2 86 may exert its pleiotropic effects through the formation of multimeric protein complexes.     

Streptomycin retards the phenotypic maturation of chick myogenic cells

Summary As part of an effort to optimize conditions required for the complete maturation of muscle cells in vitro, we have investigated the effects of the antibiotics penicillin, streptomycin, and Fungizone (amphotericin B) on the development of cultured chick embryo skeletal muscle. It is shown that even low dosages of streptomycin, but not penicillin or Fungizone, retard protein synthesis and accumulation in these cultures. Myosin accumulation was also reduced and the appearance of striations in fused cells was delayed in myotubes formed in medium containing streptomycin. Additional data suggest that this overall retardation of myogenesis is due to the influence of streptomycin on maturing myotubes rather than early proliferation and cell fusion. These results are discussed with regard to recent efforts to promote the full maturation of muscle cells grown in culture. This research was supported by National Institutes of Health Grant NS 155882 and a Task Force on Drug Development Research Contract from The Muscular Dystrophy Association.     

Effect of fatty acid modification on prostaglandin production by cultured 3T3 cells

We have investigated the extent to which modifications in the essential fatty acid content of mammalian cells can affect prostaglandin production. Swiss mouse 3T3 cells stimulated with the calcium ionophore A23187 produced 1.7 to 7 times more prostaglandin E(2) (PGE(2)) when the cultures were supplemented with linoleic acid. Increases in PGE(2) production as a result of linoleic acid supplementation occurred under all culture conditions except during the first 24 hr after attachment, when prostaglandin production was very high. Arachidonic acid supplementation produced a similar enhancement in the capacity of the cells to produce PGE(2), but no appreciable increase occurred when the cultures were supplemented with oleic acid. The phospholipids of the cells exposed to the linoleate-enriched medium contained 4 times more arachidonic acid and twice as much linoleic acid as compared with the corresponding controls. The choline phosphoglycerides were most highly enriched in arachidonic acid, but 2- to 3-fold increases also occurred in the inositol and ethanolamine phosphoglycerides. When cultures initially enriched with linoleic acid were transferred to an unsupplemented medium, the fatty acid composition as well as the capacity of the cells to produce PGE(2) reverted almost to control values. The amount of exogenous arachidonic acid converted to PGE(2) as measured by radioimmunoassay also was greater when the cells were enriched with linoleic acid. Studies with radioactive arachidonic acid indicated that the distribution of prostaglandin metabolites was not affected appreciably by linoleic acid enrichment. These findings suggest that at least two factors contribute to the increased capacity of the cultures supplemented with linoleate to produce PGE(2). One is enrichment of the phospholipid substrate pools with arachidonic acid. The other is an increased ability of the cells to synthesize PGE(2) from unesterified arachidonic acid, perhaps because the prostaglandin-forming enzymes are more active.-Denning, G. M., P. H. Figard, and A. A. Spector. Effect of fatty acid modification on prostaglandin production by cultured 3T3 cells.     

In vitro translation products specified by the transforming region of adenovirus type 2.

Region 1 DNA sequences (map positions 0 to 11% on the linear adenovirus 2 genome) are expressed both early and late in lytic infection and are required for transformation by the virus. During productive infection six distinct cytoplasmic RNAs are synthesized from this region. These RNAs comprise two families, each consisting of three size classes that share 3' sequences. Region 1 RNA's were purified by hybridization selection, using restriction fragments bound to nitrocellulose membranes, and by size fractionation. The isolated RNAs were then translated in cell-free systems derived from wheat germ and rabbit reticulocytes. The family of RNAs specified by 0 to 4.4 sequences includes two RNAs, which are 12S and 13S in size. These RNAs were partially separated by molecular weight and translated. The 13S RNA produced 53,000-dalton (53K) and 41K peptides, and the 12S RNA synthesized 47K and 35K products. The family of RNAs mapping from 4.4 to 11.0 encodes three separate polypeptides, each of which can be assigned to a specific RNA. A 12K product that comigrates with structural polypeptide IX is synthesized from the 9S RNA as previously reported (U. Pettersson and M. B. Mathews, Cell 12:741-750, 1977). The 13S RNA encodes a 15K polypeptide that corresponds to a 15K polypeptide in infected cell extracts. The 22s RNA encodes a 52K protein distinct from the 0 to 4.4 polypeptides.     

Properties of fetal and adult red blood cell arginase: a possible prenatal diagnostic test for arginase deficiency.

Prenatal diagnosis of inborn errors of metabolism has been possible only if the enzyme affected is expressed in amniotic fluid cells grown in culture. Arginase is essentially undetectable in normal human fibroblasts, amniotic fluid, and amniotic fluid cells but is present in high amounts in red blood cells. It is absent in the red blood cells of patients with liver arginase deficiency. The properties of the enzyme in the red cells of healthy children and adults were compared to those of the enzyme obtained from cord blood red cells of 13--20-week fetuses obtained at hysterotomy. The activities, heavy metal requirements, heat stability, pH optimum, kinetic properties, and reaction with anti-arginase antibody were examined. Both enzyme species were either identical or substantially similar by all criteria. The adult and fetal enzymes are, therefore, probably determined by the same structural gene. Fetal red cells obtained during amniocentesis and amnioscopy should then be a suitable tissue to use to make the prenatal diagnosis of arginase deficiency.     

Immunocytochemical localization of casein kinase II during interphase and mitosis

We have developed specific antibodies to synthetic peptide antigens that react with the individual subunits of casein kinase II (CKII). Using these antibodies, we studied the localization of CKII in asynchronous HeLa cells by immunofluorescence and immunoelectron microscopy. Further studies were done on HeLa cells arrested at the G1/S transition by hydroxyurea treatment. Our results indicate that the CKII alpha and beta subunits are localized in the cytoplasm during interphase and are distributed throughout the cell during mitosis. Further electron microscopic investigation revealed that CKII alpha subunit is associated with spindle fibers during metaphase and anaphase. In contrast, the CKII alpha' subunit is localized in the nucleus during G1 and in the cytoplasm during S. Taken together, our results suggest that CKII may play significant roles in cell division control by shifting its localization between the cytoplasm and nucleus.