Excitatory cholinergic responses in mouse primary bronchial smooth muscle require both Ca2+ entry via l-type Ca2+ channels and store operated Ca2+ entry via Orai channels.

Malfunctions in airway smooth muscle Ca2+-signalling leads to airway hyperresponsiveness in asthma and chronic obstructive pulmonary disease. Ca2+-release from intracellular stores is important in mediating agonist-induced contractions, but the role of influx via l-type Ca2+ channels is controversial. We re-examined roles of the sarcoplasmic reticulum Ca2+ store, refilling of this store via store-operated Ca2+ entry (SOCE) and l-type Ca2+ channel pathways on carbachol (CCh, 0.1-10 µM)-induced contractions of mouse bronchial rings and intracellular Ca2+ signals of mouse bronchial myocytes. In tension experiments, the ryanodine receptor (RyR) blocker dantrolene (100 µM) reduced CCh-responses at all concentrations, with greater effects on sustained rather than initial components of contraction. 2-Aminoethoxydiphenyl borate (2-APB, 100 µM), in the presence of dantrolene, abolished CCh-responses, suggesting the sarcoplasmic reticulum Ca2+ store is essential for contraction. The SOCE blocker GSK-7975A (10 µM) reduced CCh-contractions, with greater effects at higher (e.g. 3 and 10 µM) CCh concentrations. Nifedipine (1 µM), abolished remaining contractions in GSK-7975A (10 µM). A similar pattern was observed on intracellular Ca2+-responses to 0.3 µM CCh, where GSK-7975A (10 µM) substantially reduced Ca2+ transients induced by CCh, and nifedipine (1 µM) abolished remaining responses. When nifedipine (1 µM) was applied alone it had less effect, reducing tension responses at all CCh concentrations by 25% - 50%, with greater effects at lower (e.g. 0.1 and 0.3 µM) CCh concentrations. When nifedipine (1 µM) was examined on the intracellular Ca2+-response to 0.3 µM CCh, it only modestly reduced Ca2+ signals, while GSK-7975A (10 µM) abolished remaining responses. In conclusion, Ca2+-influx from both SOCE and l-type Ca2+ channels contribute to excitatory cholinergic responses in mouse bronchi. The contribution of l-type Ca2+ channels was especially pronounced at lower doses of CCh, or when SOCE was blocked. This suggests l-type Ca2+ channels might be a potential target for bronchoconstriction under certain circumstances.

Examining Relationships Between Groundwater Nitrate Concentrations in Drinking Water and Landscape Characteristics to Understand Health Risks.

Nitrate ingested from drinking water has been linked to adverse health outcomes (e.g., cancer, birth defects) at levels as low as ∼2 mg/L NO3-N, far below the regulatory limits of 10 mg/L. In many areas, groundwater is a common drinking water source and may contain elevated nitrate, but limited data on the patterns and concentrations are available. Using an extensive regulatory data set of over 100,000 nitrate drinking water well samples, we developed new maps of groundwater nitrate concentrations from 76,724 wells in Michigan's Lower Peninsula, USA for the 2006-2015 period. Kriging, a geostatistical method, was used to interpolate concentrations and quantify probability of exceeding relevant thresholds (>0.4 [common detection limit], >2 mg/L NO3-N). We summarized this probability in small watersheds (∼80 km2) to identify correlated variables using the machine learning method classification and regression trees (CARTs). We found 79% of wells had concentrations below the detection limit in this analysis (<0.4 mg/L NO3-N). In the shallow aquifer (focus of study), 13% of wells exceeded 2 mg/L NO3-N and 2% exceeded the EPA maximum contaminant level of 10 mg/L. CART explained 40%-45% of variation in each model and identified three categories of critical correlated variables: source (high agricultural nitrogen inputs), vulnerable soil conditions (low soil organic carbon and high hydraulic conductivity), and transport mechanisms (high aquifer recharge). These findings add to the body of literature seeking to identify communities at risk of elevated nitrate and study associated adverse health outcomes.

Altered sensory experience induces targeted rewiring of local excitatory connections in mature neocortex.

Experience-dependent plasticity in adulthood is slower than during development. Previous experience can accelerate adult cortical plasticity. However, the contributions of functional synaptic changes and modifications in neuronal structure to the acceleration of adult cortical plasticity remain unclear. If structural remodeling was important then it should be exhibited by neuronal connections that have altered during plasticity. We trimmed rodents' whiskers to induce experience-dependent plasticity and reconstructed pairs of layer 2/3 (L2/3) pyramidal neurons after electrophysiological recording. We reported recently that local excitatory connections strengthen without a change in synapse number in cortex with retained sensory input (spared) (Cheetham et al., 2007). Here, we show that strengthened connections are rewired. The rewiring involves remodeling of the axonal arbor of excitatory connections with only minor changes in postsynaptic dendritic trees. The axonal remodeling resulted in a greater length of presynaptic axon close to postsynaptic dendrites at existing local excitatory connections in spared cortex. In control cortex, the length of axon close to dendrite in unconnected pairs of L2/3 pyramidal neurons was similar to that in synaptically connected pairs of L2/3 pyramidal neurons. This finding suggests that the probability of forming a synapse and, therefore, establishing a connection, is not driven solely by the length of axon close to dendrite. The axonal remodeling that we describe is not associated with altered synapse number, but instead increases the number of sites where synapses could be formed between synaptically connected neurons with minimal structural changes. This enables rapid and cost-efficient rewiring of local excitatory connections when re-exposed to similarly altered sensory experience in adulthood.

Sensory experience alters cortical connectivity and synaptic function site specifically.

Neocortical circuitry can alter throughout life with experience. However, the contributions of changes in synaptic strength and modifications in neuronal wiring to experience-dependent plasticity in mature animals remain unclear. We trimmed whiskers of rats and made electrophysiological recordings after whisker cortical maps have developed. Measurements of miniature EPSPs suggested that synaptic inputs to layer 2/3 pyramidal neurons were altered at the junction of deprived and spared cortex in primary somatosensory cortex. Whole-cell recordings were made from pairs of synaptically connected pyramidal neurons to investigate possible changes in local excitatory connections between layer 2/3 pyramidal neurons. The neurons were filled with fluorescent dyes during recording and reconstructed in three dimensions using confocal microscopy and image deconvolution to identify putative synapses. We show that sensory deprivation induces a striking reduction in connectivity between layer 2/3 pyramidal neurons in deprived cortex without large-scale, compensatory increases in the strength of remaining local excitatory connections. A markedly different situation occurs in spared cortex. Connection strength is potentiated, but local excitatory connectivity and synapse number per connection are unchanged. Our data suggest that alterations in local excitatory circuitry enhance the expansion of spared representations into deprived cortex. Moreover, our findings offer one explanation for how the responses of spared and deprived cortex to sensory deprivation can be dissociated in developed animals.

LINEs.

LINEs are ubiquitous transposable elements of eukaryotes. Significant information has accumulated in the past year concerning the mechanism of transposition and the intermediates involved. In addition, progress has been made in the understanding of LINE structure and evolution, and several laboratories have exploited the interspersed, repetitive nature of LINEs for use in genome mapping.

National study of physical and sexual assault among women with disabilities.

OBJECTIVE: To examine the association between the level of disability impairment and physical and sexual assault in a sample of US women at least 18 years of age. DESIGN, SETTING AND PARTICIPANTS: Retrospective longitudinal study of 6273 non-institutionalized US women from 8000 women participating in the 1995-1996 National Violence Against Women (NVAW) Survey. MAIN OUTCOME MEASURE: Women's experiences of physical and sexual assault in the 12 months before the NVAW interview. RESULTS: Most women reported having no disability (n = 5008, 79.8%) and/or not experiencing an assault in the year before their interview (n = 6018, 95.9%). Less than 5% (n = 280) reported having a disability that severely limited daily activities, and 15.7% (n = 985) reported having a disability that moderately limited activities. Less than 4% (n = 218) of the women reported a physical-only assault, and less than 1% (n = 37) reported being sexually assaulted. Women with severe disability impairments were four times more likely to be sexually assaulted than women with no reported disabilities (RR = 4.0, 95% CI 1.5 to 10.6). Little difference in the risk of sexual assault was found between women with moderate disability impairments and those reporting no disabilities (RR = 1.0, 95% CI 0.3 to 2.8). Women with severe (RR = 1.6, 95% CI 0.9 to 3.0) and moderate (RR = 1.2, 95% CI 0.8 to 1.9) disability impairments were at greater risk, although not quite significantly so, of physical-only assault than were women without a disability. CONCLUSION: The findings suggest that women with disabilities that severely limit activities of daily living are at increased risk of sexual assault.

Tuberculosis antigen-specific immune responses can be detected using enzyme-linked immunospot technology in human immunodeficiency virus (HIV)-1 patients with advanced disease.

There are limited data on the efficacy of T cell-based assays to detect tuberculosis (TB) antigen-specific responses in immune-deficient human immunodeficiency virus (HIV) patients. The aim of this study is to determine whether TB antigen-specific immune responses can be detected in patients with HIV-1 infection, especially in those with advanced disease (CD4 T cell count < 300 cells/microl). An enzyme-linked immunospot (ELISPOT) assay, which detects interferon (IFN)-gamma secreted by T cells exposed to TB antigens, was used to assess specific immune responses in a prospective study of 201 HIV-1-infected patients with risk factors for TB infection, attending a single HIV unit. The performance of the ELISPOT assay to detect TB antigen-specific immune responses is independent of CD4 T cell counts in HIV-1 patients. The sensitivity and specificity of this assay for the diagnosis of active tuberculosis does not differ significantly from values obtained in immunocompetent subjects. The negative predictive value of the TB ELISPOT test is 98.2%. A positive predictive value of 86% for the diagnosis of active tuberculosis was found when the combined number of early secretory antigen target-6 (ESAT-6) and culture filtrate protein-10 (CFP-10) IFN-gamma spots to CD4 T cell count ratio was > 1.5. TB antigen-specific immune responses can be detected in HIV patients with low CD4 T cell counts using ELISPOT technology in a routine diagnostic laboratory and is a useful test to exclude TB infection in immune-deficient HIV-1 patients. A combination of TB antigen-specific IFN-gamma responses and CD4 T cell counts has the potential to distinguish active tuberculosis from latent infection.

Ribonucleoprotein particles with LINE-1 RNA in mouse embryonal carcinoma cells.

The LINE-1 repeat family is interspersed throughout mammalian genomes and is thought to be the result of duplicative transposition of LINE-1 sequences via an RNA intermediate. This report describes a ribonucleoprotein particle with LINE-1 RNA in the mouse embryonal carcinoma cell line F9. This ribonucleoprotein particle is a potential intermediate in the transposition of LINE-1 in the mouse genome.

Developmental and cell type specificity of LINE-1 expression in mouse testis: implications for transposition.

The LINE-1, or L1, family of interspersed repeated DNA constitutes roughly 10% of the mammalian genome. Its abundance is due to duplicative transposition via an RNA intermediate, L1-encoded proteins, and reverse transcription. Although, in principle, transposition may occur in any cell type, expression and transposition of a full-length functional element in the germ line are necessary to explain the evolutionary genetics of L1. We have found differential expression of L1 protein and RNA in germ and somatic cells of the mouse testis during development. Of particular interest is the coexpression of full-length, sense-strand L1 RNA and L1-encoded protein in leptotene and zygotene spermatocytes at postnatal day 14 of development. Expression in meiotic prophase precedes the strand breakage that occurs during chromosomal recombination; this offers an avenue for L1 insertion into new locations in chromosomal DNA in a cell type that ensures L1 propagation in future generations.

Synchronous expression of LINE-1 RNA and protein in mouse embryonal carcinoma cells.

L1, or LINE-1, is a repetitive DNA family found in all mammalian genomes that have been examined. At least a few individual members of the L1 family are functional transposable elements. Expression of these active elements leads to new insertions of L1 into the genomic DNA by the process of retrotransposition. We have detected coexpression of full-length, sense-strand L1 RNA transcripts and L1-encoded protein in mouse embryonal carcinoma cell lines. Both of these L1 expression products are candidates for intermediates in the retrotransposition process. L1 protein is found in what appear to be cytoplasmic aggregates and is not localized to any known cytoplasmic organelles. The six embryonal carcinoma cell lines tested were chosen to represent commitment to different developmental pathways in early mouse embryogenesis. The only two cell lines that express L1 are unique among the six in that they have a strong predilection to differentiate into extraembryonic endoderm. This observation is consistent with L1 expression and transposition in primordial germ cells of the mouse. An important implication of these studies is that L1 expression may provide a new marker for use in determining the origin of primordial germ cells during mouse embryogenesis.

Nucleic acid chaperone activity of the ORF1 protein from the mouse LINE-1 retrotransposon.

Non-LTR retrotransposons such as L1 elements are major components of the mammalian genome, but their mechanism of replication is incompletely understood. Like retroviruses and LTR-containing retrotransposons, non-LTR retrotransposons replicate by reverse transcription of an RNA intermediate. The details of cDNA priming and integration, however, differ between these two classes. In retroviruses, the nucleocapsid (NC) protein has been shown to assist reverse transcription by acting as a "nucleic acid chaperone," promoting the formation of the most stable duplexes between nucleic acid molecules. A protein-coding region with an NC-like sequence is present in most non-LTR retrotransposons, but no such sequence is evident in mammalian L1 elements or other members of its class. Here we investigated the ORF1 protein from mouse L1 and found that it does in fact display nucleic acid chaperone activities in vitro. L1 ORF1p (i) promoted annealing of complementary DNA strands, (ii) facilitated strand exchange to form the most stable hybrids in competitive displacement assays, and (iii) facilitated melting of an imperfect duplex but stabilized perfect duplexes. These findings suggest a role for L1 ORF1p in mediating nucleic acid strand transfer steps during L1 reverse transcription.

mRNA stability and polysome loss in hibernating Arctic ground squirrels (Spermophilus parryii).

All small mammalian hibernators periodically rewarm from torpor to high, euthermic body temperatures for brief intervals throughout the hibernating season. The functional significance of these arousal episodes is unknown, but one suggestion is that rewarming may be related to replacement of gene products lost during torpor due to degradation of mRNA. To assess the stability of mRNA as a function of the hibernation state, we examined the poly(A) tail lengths of liver mRNA from arctic ground squirrels sacrificed during four hibernation states (early and late during a torpor bout and early and late following arousal from torpor) and from active ground squirrels sacrificed in the summer. Poly(A) tail lengths were not altered during torpor, suggesting either that mRNA is stabilized or that transcription continues during torpor. In mRNA isolated from torpid ground squirrels, we observed a pattern of 12 poly(A) residues at greater densities approximately every 27 nucleotides along the poly(A) tail, which is a pattern consistent with binding of poly(A)-binding protein. The intensity of this pattern was significantly reduced following arousal from torpor and undetectable in mRNA obtained from summer ground squirrels. Analyses of polysome profiles revealed a significant reduction in polyribosomes in torpid animals, indicating that translation is depressed during torpor.

Why Helicobacter pylori has Lewis antigens.

In mimicry with human gastric epithelial cells, the lipopolysaccharide of Helicobacter pylori expresses Lewis blood group antigens. Recent data suggest that molecular mimicry does not promote immune evasion, nor does it lead to induction of autoantibodies, but that H. pylori Lewis X mediates adhesion to gastric epithelial cells and is essential for colonization.

The structures of mouse and human L1 elements reflect their insertion mechanism.

L1 is an abundant, interspersed repeated DNA element of mammalian genomes. It has achieved its high copy number via retrotransposition. Like other non-LTR retrotransposons, L1 insertion into chromosomal DNA apparently occurs by target-site primed reverse transcription, or TPRT. L1 retrotransposition often generates elements with 5' truncations that are flanked by a duplication of the genomic target site (TSD). It is typically assumed that the 5' truncated elements are the consequence of poor processivity of the L1 reverse transcriptase. However, we find that the majority of young L1 elements from both the human and mouse genomes are truncated at sequences that can basepair with the target site. Thus, to whatever extent truncation is a consequence of poor processivity, we suggest that truncation is likely to occur when target site sequence can basepair with L1 sequence. This finding supports a model for insertion that occurs by two sequential TPRT reactions, the second of which relies upon the homology between the target site and L1. Because perfect heteroduplex formation is not required for all insertions, a dynamic relationship between the primer, template and enzyme during reverse transcription is inferred. 5' truncation may be a successful evolutionary strategy that is exploited by L1 as a means to escape host suppression of transposition.

Recombination between subtypes creates a mosaic lineage of LINE-1 that is expressed and actively retrotransposing in the mouse genome.

LINE-1, or L1, elements are retrotransposons that have amplified to high-copy number during the evolution of mammals. L1 appears to amplify in waves, spawning large numbers of progeny such that elements with distinct sequence features dominate the dispersal process in a given window of time. This process generates discrete subfamilies of L1 within mammalian genomes, with the oldest being remnants, or fossils, of earlier waves of amplification. In mice, at least three distinct subfamilies of L1 were distinguished by their unique 5' ends, A, F and V. These subfamilies amplified at distinct times in the evolution of mice, with A being the youngest and V the oldest; both V and F subfamilies were believed extinct. Recent data established that a variant of the F family, TF, is actively retrotransposing. We demonstrate here that members of the TF subfamily are abundantly expressed in mouse cells and encode the major protein constituent of L1 ribonucleoprotein particles. Although members of the TF subfamily are not as numerous in the genomes of laboratory mice as are members of the older A and F subfamilies, they appear to have been activated some time ago during mouse evolution, in the common ancestor of Mus spretus and Mus domesticus. Phylogenetic analysis demonstrates that this modern, active form of TF-type L1 has a composite evolutionary history, showing evidence of multiple recombinations between distinct L1 variants, including members of the A and F subfamilies.

Deletion analysis defines distinct functional domains for protein-protein and nucleic acid interactions in the ORF1 protein of mouse LINE-1.

LINE-1, or L1, is a non-LTR retrotransposon in mammals. Retrotransposition of L1 requires the action of two element-encoded proteins, ORF1p and ORF2p. ORF2p provides essential enzymatic activities for the reverse transcription and integration of a newly transposed copy of L1, whereas the exact role of ORF1p is less well understood. The 43 kDa ORF1p copurifies as a large complex with L1 RNA in extracts of human and mouse cells. Mouse ORF1p purified from Escherichia coli binds RNA and single-stranded DNA in vitro, exhibits nucleic acid chaperone activity, and is capable of protein-protein interaction. In this study we create a series of deletions in the ORF1 sequence, express the truncated proteins and examine their activities to delineate the region of ORF1p responsible for these different functions. By both yeast two-hybrid analysis and GST pull-down assay, the protein-protein interaction domain is defined as a coiled-coil domain that encompasses about one third of the protein near its N terminus. Based on data obtained with UV-cross-linking, electrophoretic mobility-shift assay and an annealing assay, the C-terminal one third of ORF1p is both necessary and sufficient for nucleic acid binding and to promote annealing of complementary oligonucleotides. Separation of these activities into different domains of ORF1p will facilitate detailed biochemical analyses of the structure and function of this protein and understanding of its role during L1 retrotransposition.

Rise and fall of the delta globin gene.

This paper examines the molecular basis for the origin and subsequent silencing of the delta globin gene during the evolution of higher primates. We cloned and sequenced the delta gene from representatives of the two most distantly related types of Old World monkeys in which the gene is silent. The silent delta genes of these two monkeys (rhesus and colobus) are highly homologous to each other (97.5%) and to the functional human delta gene (94%). The presumed mutation that silenced the delta gene is therefore unlikely to be obscured by later mutations at the same site. This silencing mutation could have affected transcription since we find no delta transcript in rhesus bone marrow. Furthermore, the delta globin genes from colobus and rhesus monkeys are many times less efficient than the human delta gene in a cell-free transcription assay. The two Old World monkeys share only three nucleotide substitutions in the first 100 base-pairs of the DNA sequence 5' to the site for initiation of transcription when compared to human delta. It is likely that the in vitro silencing of the delta gene was brought about by one (or a combination) of these three substitutions. Three analysis shows how the delta sequences are related to those for other beta-like genes, including the colobus beta gene whose sequence we report. One part of the delta gene appears to be derived from a (pseudo?) beta gene that diverged from beta before the divergence of mice and men. The other part is closely related to the beta gene of higher primates. The mosaic nature of the delta gene is apparently due to a partial conversion which took place between the pseudo beta and the functional beta gene before the divergence of the lineages leading to Old World monkeys and hominoids.

Dispersal process associated with the L1 family of interspersed repetitive DNA sequences.

We have determined the complete nucleotide sequence for five members of the L1Md repetitive family from the beta-globin gene region of the BALB/c mouse. The five repeats are different lengths, each terminating at the 5' end at different points with respect to one another. We have analyzed the nucleotides around the endpoints of the five repeats for clues as to the mechanisms involved with the dispersal and 5' truncation of this repeat family. Each L1 member is flanked by a pair of short direct repeats. Since these direct repeats differ in length and sequence in each of the five cases, the dispersal mechanism does not involve a sequence targeted process. The sequence at the 3' end is conserved and its organization resembles the 3' end of a polyadenylated RNA, suggesting that transcripts of the repeat are involved in the dispersal process either directly or as intermediates in the generation of complementary DNA copies of the sequence. One of the L1 repeats is a recent insertion, since it is found in the Hbbd chromosome, but not in the Hbbs chromosome. This suggests a dispersal process that has been active as recently as 4 million years ago.

Conservation throughout mammalia and extensive protein-encoding capacity of the highly repeated DNA long interspersed sequence one.

We report an investigation of the structure, evolutionary history, and function of the highly repeated DNA family named Long Interspersed Sequence One (L1). Hybridization studies show, first, that L1 is present throughout marsupial and placental mammalian orders. Second, L1 is more homologous within these species than between them, which suggests that it has undergone concerted evolution within each mammalian lineage. Third, on the whole L1 diverges in accordance with the fossil record. This suggests that it arose in each lineage rather by inheritance from a common ancestral family, which was present in the progenitor to mammals, than by cross-species transmission. Alignment of 1.6 X 10(3) bases of primate and mouse L1 DNA sequences shows a predominance of silent mutations within aligned long open reading frames, indicating that at least this part of L1 has produced functional protein. The observation of additional long open reading frames in further unaligned DNA sequences suggests that a minimum of 3.2 X 10(3) bases or at least half of the L1 structure is a protein-coding sequence. Thus L1, which contains about 100,000 members in mouse, is by far the most repetitive family of which a subset comprises functional protein-encoding genes. The ability of the putative protein-encoding regions of mouse L1 to hybridize to L1 homologs throughout the Mammalia implies that these sequences have been subject to conservative selection upon protein function in all mammalian lineages, rather than in a few. L1 is therefore a highly repeated family of genes with both a widespread and an ancient history of function in mammals.