Socially isolated? How parents and neighbourhood adults influence youth behaviour in disadvantaged communities

William Julius Wilson’s model of adult joblessness, community disorganization and their effects on youth problem behaviour de-emphasizes the range in children’s outcomes across socially disorganized communities, and says little about the factors that influence this variation. It also does not address the processes by which family structure and relationships affect the well-being of African-American and poor youth. My work is part of a larger research agenda that has begun to address these issues by focusing on the differential rates of sexual activity among youth living in disadvantaged environments, and developing models to explain this variation. This work suggests that units of socially cohesive, stable adults exist among the social networks of successful children and families in poor neighbourhoods. It also points to the existence and functioning of alternative two-parent family structures and offers hypotheses for how family environment interacts with neighbourhood context to influence youth behaviour.     

Identification,purification, and characterization of pathogenesis-related proteins from virus-infected Samsun NN tobacco leaves

Ten pH-3 soluble, low-molecular-weight pathogenesis-related proteins (PRs) were found to accumulate in leaves of tobacco cv. Samsun NN reacting hypersensitively to tobacco mosaic virus. Besides the previously characterized PRs 1a, 1b, 1c and 2, these proteins were provisionally designated N, O, P, Q, R, and S in order of decreasing electrophoretic mobility in native polyacrylamide gels. Two-dimensional gel electrophoresis indicated that the PRs consist of single polypeptides, except for R, which is composed of two components with slightly different molecular weights. Estimated molecular weights in SDS-containing gels were: PRs 1a and 1b 17 kD, 1c 16.5 kD, 2 31 kD, N 33 kD, O 35 kD, P 27 kD, Q 28 kD, R 13 and 15 kD, and S 25 kD. However, based on their elution from gel filtration columns and relative moblities in native gels of different acrylamide concentrations, P and Q appeared to have molecular weights similar to those of the PR 1 group. Upon chromatofocusing no additional components were resolved. The PRs were eluted between pH 7 and 4; except for R, their pIs, as judged from isoelectric focusing, appeared to lie in the range from pH 4 to 5.2. In the presence of 6 M urea PR 1a was split into two components, one of which was strongly retarded on gels, as were P and Q. None of the PRs was detected when gels were stained for glycoproteins.By combinations of gel filtration, DEAE-cellulose chromatography, and chromatofocusing, PRs 1a, 1b, 1c, 2 and N were purified, their amino acid compositions determined, and antisera raised against each of these components. By Western blotting, antisera against either PR 1a, 1b, or 1c reacted with each of the components of the PR 1 group, as well as with PR S. Similarly, the antisera against either PR 2 or N reacted with both 2 and N, as well as with O and R. On the basis of major similarities in molecular weight characteristics, amino acid compositions, and serological relationships, it is proposed to classify tobacco PRs into five groups: 1: PRs 1a, 1b, and 1c; 2: 2a (formerly 2), 2b (N), and 2c (O); 3: 3a (P), and 3b (Q); 4: 4a and 4b (the two components of R); and 5: PR 5 (S).     

Ethylene production by loblolly pine seedlings associated with water stress

Effects of water stress on production of ethylene and its precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), by loblolly pine ( Pinus taeda L.) seedlings from a Texas drought-hardy and a Virginia Coastal Plain source were investigated. Ethylene production rates in needles from the Virgnia source increased slightly with initial stress (-1.3 MPa), declined until water potential reached -1.6 MPa and then increased sharply at -2.5 MPa. The ethylene production rates in needles from the Texas also increased slightly with initial stress, then decreased with decreasing water potential. Ethylene production by root tissue was two to three times higher than needle tissue and decreased with decreasing water potential. ACC concentrations in needles of both seed sources decreased as water potential began decreasing. Below -1.4 MPa, ACC levels started increasing (Texas source) or remained constant until -2.8 MPa (Virginia source) at which time its level increased three-fold. Mean ACC levels in root tissue [122 nmol (g dry weight)⁻¹] were slightly higher than the mean levels in the needle tissue [92 nmol (g dry weight) ⁻¹]; roots apparently were more efficient in converting it to ethylene since ethylene production was two to three times higher than needle tissue. The modulation of ethylene synthesis by ACC synthase and ethyleneforming enzyme appeared to be influenced by stress level, organ and seed source.     

Evolution of chorion structural genes and regulatory mechanisms in two wild silkmoths: A preliminary analysis

Summary We report a preliminary analysis of structural and regulatory evolution of the A and B chorion gene families in two wild silkmoths,Antheraea pernyi andAntheraea polyphemus. Homospecific and heterospecific dot hybridizations were performed between previously characterizedA. polyphemus complementary DNA clones and total or stage-specific follicular mRNAs from the two species. The hybridization patterns indicated substantial interspecies changes in the abundance of corresponding mRNA sequences (heteroposic evolution) without substantial changes in their developmental specificities (heterochronic evolution). In addition, the proteins encoded in the two species by corresponding mRNAs were determined by hybrid-selected translation followed by electrophoretic analysis. The results suggested that the proteins evolve in size, presumably through internal deletions and duplications.     

Structural implications of primary sequences from a family of Balbiani ring-encoded proteins inChironomus

Summary DNA sequencing has revealed an internal, tandemly repetitive structure in the family of giant polypeptides encoded by three types of Balbiani ring (BR) genes, in three different species ofChironomus. Each major BR repeat can be subdivided into two halves: a region consisting of short subrepeats and a more constant region that lacks obvious subrepeats. Comparative predictions of secondary structure indicate that an -helical segment is consistently present in the amino-terminal half of the constant region in all known BR proteins. Comparative predictions, coupled with consideration of the known phosphorylation of serine and threonine residues in BR proteins, suggest that the -helical structure may also extend into the carboxy-terminal half of the constant region, possibly interrupted by -turn(s). However, it is also possible that the structure is variable, and that a -strand is present in that half in some cases. All of the constant regions conserve one methionine and one phenylalanine residue, as well as all four cysteines; these residues presumably play roles in the packing or cross-linking of aligned constant regions. The structure of the subrepeat region is not clear, but the prevalence of a tripeptide pattern (basic-proline-acidic) suggests some type of structural regularity, possibly an extended helix. The possible significance of these conserved molecular features is discussed in the context of how they may serve the elasticity, insolubility, and hydrophilicity of the fibrils and threads formed by the BR polypeptides.     

Growth, dry weight partitioning and wood properties of Pinus radiata D. Don after 2 years of CO2 enrichment

Abstract Advanced selections (families 20010 and 20062) of P. radiata D. Don were exposed to either 340 or 660 μmol CO₂ mol ¹ for 2 years to establish if growth responses to high CO₂ would persist during the development of woody tissues. The experiment was carried out in glasshouses and some of the trees at each CO₂ concentration were subjected to phosphorus deficiency and to periodic drought. CO₂ enrichment increased whole-plant dry matter production irrespective of water availability, but only when phosphorus supply was adequate. The greatest increase occurred during the exponential period of growth and appeared to be tied to increased rates of photosynthesis, which caused accelerated production of leaf area. The increase in whole-plant dry matter production was similar for both families; however, family 20010 partitioned larger amounts of dry weight to the trunks than family 20062. which favoured the roots and branches. Wood density was generally increased by elevated CO₂ and for family 20010 this increase was due to thickening of the tracheid walls. Tracheid length was similar at both CO₂ levels but differed between families. These results suggest that, as the atmospheric CO₂ concentration rises, field-grown P. radiata should produce more dry weight at sites where phosphorus is not acutely deficient, even where drought limits growth; however, increases in wood production are likely only for genotypes which continue to partition at least the same proportion of dry weight to wood in the trunk.     

Members of two gene families encoding ubiquitin-conjugating enzymes, AtUBC1-3 and AtUBC4-6, fromArabidopsis thaliana are differentially expressed

Covalent attachment of ubiquitin to other intracellular proteins is essential for many physiological processes in eukaryotes, including selective protein degradation. Selection of proteins for ubiquitin conjugation is accomplished, in part, by a group of enzymes designated E2s or ubiquitin-conjugating enzymes (UBCs). At least six types of E2s have been identified in the plantArabidopsis thaliana; each type is encoded by a small gene family. Previously, we described the isolation and characterization of two three-member gene families, designatedAtUBC1-3 andAtUBC4-6, encoding two of these E2 types. Here, we investigated the expression patterns, of theAtUBC1-3 andAtUBC4-6 genes by the histochemical analysis of transgenicArabidopsis containing the corresponding promoters fused to the -glucuronidase-coding region. Staining patterns showed that these genes are active in many stages of development and some aspects of cell death, but are not induced by heat stress. Within the two gene families, individual members exhibited both overlapping and complementary expression patterns, indicating that at least one member of each gene family is expressed in most cell types and at most developmental stages. Different composite patterns of expression were observed between theAtUBC1-3 andAtUBC4-6 families, suggesting distinct biochemical and/or physiological functions for the encoded E2s inArabidopsis.     

Phylogenetic analysis of the stress-70 protein family

The eukaryotic cyto-/nucleoplasmatic 70-kDa heat-shock protein (HSP70) has homologues in the endoplasmic reticulum as well as in bacteria, mitochondria, and plastids. We selected a representative subset from the large number of sequenced stress-70 family members which covers all known branches of the protein family and calculated and manually improved an alignment. Here we present the consensus sequence of the aligned proteins and putative nuclear localization signals (NLS) in the eukaryotic HSP70 homologues. The phylogenetic relationships of the stress-70 group family members were estimated by use of different computation methods. We present a phylogenetic tree containing all known stress-70 subfamilies and demonstrate the usefulness of stress-70 protein sequences for the estimation of intertaxonic phylogeny. Correspondence to: S.A. Reusing     

Structure of the smallest salivary-gland secretory protein gene in Chironomus tentans

The salivary gland secretion in the dipteran Chironomus tentans is composed of approximately 15 different secretory proteins. The most well known of the corresponding genes are the four closely related Balbiani ring (BR) genes, in which the main part of each approximately 40-kb gene is composed of tandemly arranged repetitive units. Six of the seven additional secretory protein genes described share structural similarities with the BR genes and are members of the same BR multigene family. Here we report the identification of a new secretory protein gene, the spl2 gene, encoding the smallest component of the C. tentans salivary gland secretion. The gene has a corresponding mRNA length of approximately 0.7 kb and codes for a protein with a calculated molecular weight of 7,619 Da. The sp12 gene was characterized in seven Chironomus species. Based on a comparison of the orthologous gene sequences, we conclude that the sp12 gene has a repetitive structure consisting of diverged 21-by-long repeats. The repeat structure and the codon composition are similar to the so-called SR regions of the BR genes and the sp 12 gene may represent a diverged member of the BR multigene family. Correspondence to: L. Wieslander