HIV replication in CD4+ T lymphocytes in the presence and absence of follicular dendritic cells: inhibition of replication mediated by α-1-antitrypsin through altered IκBα ubiquitination

Follicular dendritic cells (FDCs) increase HIV replication and virus production in lymphocytes by increasing the activation of NF-κB in infected cells. Because α-1-antitrypsin (AAT) decreases HIV replication in PBMCs and monocytic cells and decreases NF-κB activity, we postulated that AAT might also block FDC-mediated HIV replication. Primary CD4(+) T cells were infected with HIV and cultured with FDCs or their supernatant with or without AAT, and ensuing viral RNA and p24 production were monitored. NF-κB activation in the infected cells was also assessed. Virus production was increased in the presence of FDC supernatant, but the addition of AAT at concentrations >0.5 mg/ml inhibited virus replication. AAT blocked the nuclear translocation of NF-κB p50/p65 despite an unexpected elevation in associated phosphorylated and ubiquitinated IκBα (Ub-IκBα). In the presence of AAT, degradation of cytoplasmic IκBα was dramatically inhibited compared with control cultures. AAT did not inhibit the proteasome; however, it altered the pattern of ubiquitination of IκBα. AAT decreased IκBα polyubiquitination linked through ubiquitin lysine residue 48 and increased ubiquitination linked through lysine residue 63. Moreover, lysine reside 63-linked Ub-IκBα degradation was substantially slower than lysine residue 48-linked Ub-IκBα in the presence of AAT, correlating altered ubiquitination with a prolonged IκBα t(1/2). Because AAT is naturally occurring and available clinically, examination of its use as an inhibitory agent in HIV-infected subjects may be informative and lead to the development of similar agents that inhibit HIV replication using a novel mechanism.     

A novel mechanism of G protein-coupled receptor functional selectivity. Muscarinic partial agonist McN-A-343 as a bitopic orthosteric/allosteric ligand

Many G protein-coupled receptors (GPCRs) possess allosteric binding sites distinct from the orthosteric site utilized by their cognate ligands, but most GPCR allosteric modulators reported to date lack signaling efficacy in their own right. McN-A-343 (4-(N-(3-chlorophenyl)carbamoyloxy)-2-butynyltrimethylammonium chloride) is a functionally selective muscarinic acetylcholine receptor (mAChR) partial agonist that can also interact allosterically at the M(2) mAChR. We hypothesized that this molecule simultaneously utilizes both an allosteric and the orthosteric site on the M(2) mAChR to mediate these effects. By synthesizing progressively truncated McN-A-343 derivatives, we identified two, which minimally contain 3-chlorophenylcarbamate, as pure allosteric modulators. These compounds were positive modulators of the orthosteric antagonist N-[(3)H]methylscopolamine, but in functional assays of M(2) mAChR-mediated ERK1/2 phosphorylation and guanosine 5'-3-O-([(35)S]thio)triphosphate binding, they were negative modulators of agonist efficacy. This negative allosteric effect was diminished upon mutation of Y177A in the second extracellular (E2) loop of the M(2) mAChR that is known to reduce prototypical allosteric modulator potency. Our results are consistent with McN-A-343 being a bitopic orthosteric/allosteric ligand with the allosteric moiety engendering partial agonism and functional selectivity. This finding suggests a novel and largely unappreciated mechanism of "directed efficacy" whereby functional selectivity may be engendered in a GPCR by utilizing an allosteric ligand to direct the signaling of an orthosteric ligand encoded within the same molecule.     

Microsatellite loci from the northern house mosquito (Culex pipiens), a principal vector of West Nile virus in North America

Microsatellites were isolated and characterized in the northern house mosquito, Culex pipiens, a widespread pest species and important vector of diseases such as West Nile virus. An enrichment protocol yielded 150 positive clones. We designed primers to amplify 17 unique (GT)_n microsatellites, eight of which amplified cleanly and were polymorphic. A survey of 29 individuals showed that these loci are highly variable with the number of alleles ranging from seven to 19 and expected heterozygosity ranging from 0.66 to 0.93. These markers will be useful for studies of population structure and intraspecific variation in epidemiological characteristics of Cx. pipiens.     

Sex differences in the response to environmental cues regulating seasonal reproduction in birds

Although it is axiomatic that males and females differ in relation to many aspects of reproduction related to physiology, morphology and behaviour, relatively little is known about possible sex differences in the response to cues from the environment that control the timing of seasonal breeding. This review concerns the environmental regulation of seasonal reproduction in birds and how this process might differ between males and females. From an evolutionary perspective, the sexes can be expected to differ in the cues they use to time reproduction. Female reproductive fitness typically varies more as a function of fecundity selection, while male reproductive fitness varies more as a function sexual selection. Consequently, variation in the precision of the timing of egg laying is likely to have more serious fitness consequences for females than for males, while variation in the timing of recrudescence of the male testes and accompanying territory establishment and courtship are likely to have more serious fitness consequences for males. From the proximate perspective, sex differences in the control of reproduction could be regulated via the response to photoperiod or in the relative importance and action of supplementary factors (such as temperature, food supply, nesting sites and behavioural interactions) that adjust the timing of reproduction so that it is in step with local conditions. For example, there is clear evidence in several temperate zone avian species that females require both supplementary factors and long photoperiods in order for follicles to develop, while males can attain full gonadal size based on photoperiodic stimulation alone. The neuroendocrine basis of these sex differences is not well understood, though there are many candidate mechanisms in the brain as well as throughout the entire hypothalamo-pituitary-gonadal axis that might be important.     

Spread and persistence of a rugulosin-producing endophyte in Picea glauca seedlings

We have studied Picea glauca (white spruce) endophyte colonization and its affect on the growth of Choristoneura fumiferana (spruce budworm). Here we examine the spread and persistence of a rugulosin-producing endophyte and rugulosin in needles from trees maintained in the nursery, as well as in trees planted in a test field site. Additionally, we report toxicity of rugulosin against three P. glauca needle herbivores: C. fumiferana, Lambdina fiscellaria (hemlock looper) and Zeiraphera canadensis (spruce budmoth). Reduction in body weight for both the C. fumiferana and L. fiscellaria were observed at 25 and 50 μm, respectively, and head capsules were reduced at 100 and 150 μm. Z. canadensis larvae did not perform as well in tests due to an Aspergillus fumigatus infection, but were shown to be lighter when tested with 100 and 150 μm compared with controls. The endophyte and its toxin were shown to spread throughout the nursery-grown seedlings. After 3.5 and 4.5 y post-inoculation (one and two years in the test site), the inoculated endophyte and its toxin had remained present with an average rugulosin concentration of 1 μg g⁻¹.     

Quantitation of Rat Dopamine Transporter mRNA: Effects of Cocaine Treatment and Withdrawal

Dopamine transporter mRNA levels in the rat substantia nigra were quantified using a sensitive nuclease protection assay with a highly homologous human dopamine transporter cDNA clone. The same probe was also used to visualize dopamine transporter mRNA in the substantia nigra by in situ hybridization. Repeated cocaine administration (15 mg/kg, twice a day for 6.5 days) resulted in a greater than 40% decrease in nigral dopamine transporter mRNA levels. In contrast, dopamine transporter mRNA levels were unchanged after either acute treatment (4 h before death) or repeated cocaine treatment followed by a 72-h withdrawal period. Thus, blockade of the dopamine transporter by repeated cocaine administration may result in the down-regulation of dopamine transporter gene expression in dopamine neurons.     

Anchoring a cationic ligand: the structure of the Fab fragment of the anti-morphine antibody 9B1 and its complex with morphine

The crystal structures of an anti-morphine antibody 9B1 (to 1.6A resolution) and its complex with morphine (to 2.0 A resolution) are reported. The morphine-binding site is described as a shallow depression on the protein surface, an unusual topology for a high-affinity ( Ka approximately 10(9) M(-1)) antibody against a small antigen. The polar part of the ligand is exposed to solvent, and the cationic nitrogen atom of the morphine molecule is anchored at the bottom of the binding site by a salt-bridge to a glutamate side-chain. Additional affinity is provided by a double cation-pi interaction with two tryptophan residues. Comparison of the morphine complex with the structure of the free Fab shows that a domain closure occurs upon binding of the ligand.     

Genomic DNA sequence of Rhesus (M. mulatta) cystic fibrosis (CFTR) gene

Cystic fibrosis is a common human genetic disease caused by mutations in CFTR, a gene that codes for a chloride channel that is regulated by phosphorylation and cytosolic nucleotides. As part of a program to discover natural animal models for human genetic diseases, we have determined the genomic sequence of CFTR in the Rhesus monkey, Macaca mulatta. The coding region of rhesus CFTR is 98.3% identical to human CFTR at the nucleotide level and 98.2% identical and 99.7% similar at the amino acid level. Partial sequences of flanking introns (5582 base pair positions analyzed) revealed 91.1% identity with human introns. Relative to rhesus intronic sequence, the human sequences had 27 insertions and 22 deletions. Primer sequences for amplification of rhesus genomic CFTR sequences are provided. The accession number is AF013753 (all 27 exons and some flanking intronic sequence). Received: 27 August 1992 / Accepted: 5 December 1997     

Age and sex dimorphisms contribute to the severity of bleomycin-induced lung injury and fibrosis

Fibrotic interstitial pneumonias are more prevalent in males of advancing age, although little is known about the underlying mechanisms. To evaluate the contributions of age and sex to the development of pulmonary fibrosis, we intratracheally instilled young (8-12 wk) and aged (52-54 wk) male and female mice with bleomycin and assessed the development and severity of fibrotic lung disease by measurements of lung collagen levels, static compliance, leukocyte infiltration, and stereological quantification of fibrotic areas in histological sections. We also quantified proinflammatory and profibrotic chemokine and cytokine levels in the bronchoalveolar lavage fluid. Aged male mice developed more severe lung disease, indicated by increased mortality, increased collagen deposition, and neutrophilic alveolitis compared with aged female mice or young mice of either sex. Aged male mice also exhibited increased levels of transforming growth factor-β, IL-17A, and CXCL1 in their bronchoalveolar lavage fluid. Young male mice developed a more fibrotic disease after bleomycin instillation compared with female mice, regardless of age. There was no difference in fibrosis between young and aged female mice. Taken together, these findings suggest that the variables of advanced age and male sex contribute to the severity of pulmonary fibrosis in this model. Our findings also emphasize the importance of stratifying experimental groups on the basis of age and sex in experimental and epidemiological studies of this nature.     

Stem cell ageing and non-random chromosome segregation

Adult stem cells maintain the mature tissues of metazoans. They do so by reproducing in such a way that their progeny either differentiate, and thus contribute functionally to a tissue, or remain uncommitted and replenish the stem cell pool. Because ageing manifests as a general decline in tissue function, diminished stem cell-mediated tissue maintenance may contribute to age-related pathologies. Accordingly, the mechanisms by which stem cell regenerative potential is sustained, and the extent to which these mechanisms fail with age, are fundamental determinants of tissue ageing. Here, we explore the mechanisms of asymmetric division that account for the sustained fitness of adult stem cells and the tissues that comprise them. In particular, we summarize the theory and experimental evidence underlying non-random chromosome segregation-a mitotic asymmetry arising from the unequal partitioning of chromosomes according to the age of their template DNA strands. Additionally, we consider the possible consequences of non-random chromosome segregation, especially as they relate to both replicative and chronological ageing in stem cells. While biased segregation of chromosomes may sustain stem cell replicative potential by compartmentalizing the errors derived from DNA synthesis, it might also contribute to the accrual of replication-independent DNA damage in stem cells and thus hasten chronological ageing.