Dynamical Systems Approach to Higher-level Heritability

To explain higher-level heritability, we propose a dynamical systems approach, based on simulations of the high-dimensional replicator equation with mutation dynamics. We assume that all variants are generated from within the groups of variants through mutations. Simulating the equation with a random interaction matrix and possible variants, we report that this system tends to have many attractors, of fixed point, chaotic and quasiperiodic type. In a chaotic attractor, special gene-like variants appear to control the heritability ofthe system, in the sense that removal of the variants would easily enable the system to depart from the attractor. Those variants do not predominate in thepopulation size, but have the lowest net reproduction and mutation rates on average. Because their rate of growth is small, they are named neutral phenotypes. Additionally, combinatorial effects of these neutral variants to the entire system are reported.     

Potentiation of growth suppression and modulation of the antigenic phenotype in human melanoma cells by the combination of recombinant human fibroblast and immune interferons

Summary Administration of interferon as a single therapeutic regimen in cancer patients with various neoplasias has had only limited efficacy in ameliorating the negative clinical course of their disease. In the present study, we have evaluated the effect of recombinant human fibroblast (IFN) and immune (IFN) interferon, alone and in combination, on growth, differentiation and the expression of class I and II histocompatibility locus antigens (HLA) and melanoma-associated antigens on the human melanoma cell line H0-1. The effect of combinations of interferons on the antigenic profile of human melanoma cells displaying different organ colonization and spontaneous metastatic potential in athymic nude mice was also determined. H0-1 cells were more sensitive to the antiproliferative activity of IFN than to IFN and the combination of interferons resulted in a potentiation of growth suppression. The antiproliferative effect of both interferons was greater in later-passage than in earlier-passage H0-1 cells, possibly reflecting alterations in the evolving tumor cell population as a result of long-term in vitro propagation and/or the selective outgrowth of cells with an increased growth rate. The enhanced growth suppression observed in H0-1 cells treated with the combination of IFN plus IFN was not associated with a significant increase in the level of melanin, a marker of melanoma differentiation, above that observed with either interferon used alone. IFN and IFN differentially modulated the expression of class I and II HLA and melanoma-associated antigens in H0-1 cells and a series of melanoma cells with different organ colonization and metastatic potential, including MeWo, MeM 50-10, MeM 50-17, 3S5 and 70W. No consistent potentiation or antagonism in the expression of any specific antigen was observed in any of the melanoma cell lines exposed to the combination of interferons. The present study demonstrates that the combination of IFN plus IFN can potentiate growth suppression in H0-1 human melanoma cells and that this effect is not associated with an increase in differentiation or a potentiation in antigenic modulation. In addition, no direct correlation between the expression of any specific antigen or its modulation by IFN or IFN, alone or in combination, and organ colonization and metastatic potential in nude mice was observed in the different melanoma cell lines.     

Segments of chromosomal DNA from Rhynchosciara americana that undergo additional rounds of DNA replication in the salivary gland DNA puffs have only weak ARS activity in yeast

We have constructed a library of recombinant phage containing DNA from salivary gland chromosomes of Rhynchosciara americana. We have isolated phage from this library that carry sequences homologous to cDNA clones that hybridize in situ to the DNA puffs at the polytene chromosome regions C3 and C8. This has enabled us to demonstrate a 16-fold amplification of the genomic DNA sequences at these regions during DNA-puffing. At the C8 site there is a sequence element that has characteristics of 'scrambled' moderately repetitive DNA. This is located within 3 kb from the gene encoding a 1.95-kb mRNA. We have assayed restriction fragments from the two DNA puffs for Ars activity in yeast. The only strong Ars activity is associated with a part of the moderately repetitive DNA element from the C8 puff which is not present at this site in all animals.     

Intracellular features of type II procollagen and chondroitin sulfate proteoglycan synthesis in chondrocytes

The intracellular compartments of chondrocytes involved in the synthesis and processing of type II procollagen and chondroitin sulfate proteoglycan (CSPG) monomer were investigated using simultaneous double immunofluorescence and lectin localization reactions. Type II procollagen was distributed in vesicles throughout the cytoplasm, whereas intracellular precursors of CSPG monomer were accumulated in the perinuclear cytoplasm. In this study, cytoplasmic vesicles that stained intensely with antibodies directed against CSPG monomer but did not react with type II collagen antibodies, also were observed. A monoclonal antibody, 5-D-4, that recognizes keratan sulfate determinants was used to identify the Golgi complex (the site of keratan sulfate chain elongation). Staining with 5-D-4 was restricted to the perinuclear cytoplasm. The vesicles outside the perinuclear cytoplasm that stained intensely with antibodies to CSPG monomer did not react with 5-D-4. Fluorescent lectins were used to characterize further subcellular compartments. Concanavalin A, which reacts with mannose-rich oligosaccharides, did not stain the perinuclear region, but it did stain vesicles throughout the rest of the cytoplasm. Because mannose oligosaccharides are added cotranslationally, the stained vesicles throughout the cytoplasm presumably correspond to the rough endoplasmic reticulum. Wheat germ agglutinin, which recognizes N-acetyl-D-glucosamine and sialic acid (carbohydrates added in the Golgi), stained exclusively the perinuclear cytoplasm. By several criteria (staining with the monoclonal antibody 5-D-4 and with wheat germ agglutinin), the perinuclear cytoplasm seems to correspond to the Golgi complex. The cytoplasmic vesicles that react with anti-CSPG monomer and not with anti-type II collagen contain precursors of CSPG monomer not yet modified by Golgi-mediated oligosaccharide additions (because they are not stained with wheat germ agglutinin or with the anti-keratan sulfate antibody); these vesicles may have a unique function in the processing of CSPG.     

Deposition of type X collagen in the cartilage extracellular matrix

In cultured chick embryo chondrocytes, type X collagen is preferentially deposited in the extracellular matrix, the ratio between type II and type X collagen being about 5 times higher in the culture medium than in the cell layer. When the newly synthesized collagens deposited in slices from the epiphyseal cartilage of 17-day-old embryo tibiae were isolated, type X collagen was always the major species. In agreement with this result the mRNA for type X collagen was the predominant mRNA species purified from the same tissue. When the total collagen (unlabeled) deposited in the epiphyseal cartilage was analyzed, it was observed that type X collagen represented only 1/15 of the type II collagen recovered in the same preparation. The possible explanations for these differences are discussed.     

The S11 and S13 self incompatibility alleles in Solanum chacoense Bitt. are remarkably similar

A genomic clone of the S11 allele from the self-incompatibility locus (S locus) in Solanum chacoense Bitt. has been isolated by cross-hybridization to the S. chacoense S13 allele and sequenced. The sequence of the S11 allele contains all the features expected for S genes of the Solanaceae, and S11 expression, as assessed by northern blots and RNA-PCR, was similar to that of other S. chacoense S alleles. The S11 protein sequence shares 95% identity with the phenotypically distinct S13 protein of S. chacoense and is the gametophytic S allele with the highest similarity to an existing allele so far discovered. Only 10 amino acid changes differentiate the mature proteins from these two alleles, which sets a new lower limit to the number of changes that can produce an altered S allele specificity. The amino acid substitutions are not clustered, suggesting that an accumulation of random point mutations can generate S allele diversity. The S11 intron is unusual in that it could be translated in frame with the coding sequence, thus suggesting an additional mechanism for the generation of new S alleles.     

Human bone marrow stromal cells express an osteoblastic phenotype in culture

Summary This study reports the selection and characterization of osteogenic precursors from human bone marrow which were isolated by two “clonings” and successive subculturing. These cell lines express alkaline phosphatase activity. Gel electrophoresis of [³H]-proline labeled cultures showed that the cloned cells produce only type I collagen. They synthetize osteocalcin and osteonectin. They respond to 1,25 dihydroxy vitamin D₃ by increasing osteocalcin synthesis and secretion, and to parathyroid hormone by increasing cyclic AMP synthesis. After the third subculture in the absence of β-glycerophosphate, these cell lines formed lots of clusters which exhibit high alkaline phosphatase activity and positive von Kossa staining. X-ray energy spectrum shows that these cells are surrounded by “budding” structures containing calcium and phosphorus with a ratio Ca:P identical to those of pure hydroxyapatite. This process was associated with⁴⁵Ca uptake into the cells. All these data support the selection of osteogenic cells which may be of considerable clinical importance.